For the etc/NEWS file, I don't know where this would fit, so it's not
a patch.

A new attribute `min-colors' has been added to the `defface' face
specification language. It is used to specify the face characteristics
depending on the number of colors supported by the display.


lisp/ChangeLog
2004-02-12  Dan Nicolaescu  <dann@ics.uci.edu>

	* faces.el (face-spec-set-match-display): Add a new  attribute,
	`min-colors'. 
	(region, highlight, secondary-selection): Use `min-colors`.

	* custom.el (defface): Add documentation for `min-colors'.

	* font-lock.el (font-lock-comment-face, font-lock-string-face,
	font-lock-keyword-face, font-lock-function-name-face,
	font-lock-variable-name-face, font-lock-constant-face): Use
	`min-colors`.

	* isearch.el (isearch, isearch-lazy-highlight-face): Use
	`min-colors'. 

lispref/ChangeLog

2004-02-12  Dan Nicolaescu  <dann@ics.uci.edu>

	* display.texi (Defining Faces): Add description for min-colors.


Index: lisp/faces.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/faces.el,v
retrieving revision 1.280
diff -c -3 -p -r1.280 faces.el
*** lisp/faces.el	1 Sep 2003 15:45:11 -0000	1.280
--- lisp/faces.el	12 Feb 2004 21:42:10 -0000
*************** If FRAME is nil, the current FRAME is us
*** 1314,1319 ****
--- 1314,1321 ----
  				  (not (featurep 'motif)))
  			     (and (memq 'x-toolkit options)
  				  (featurep 'x-toolkit))))
+ 			((eq req 'min-colors)
+ 			 (>= (display-color-cells frame) (car options)))
  			((eq req 'class)
  			 (memq (frame-parameter frame 'display-type) options))
  			((eq req 'background)
*************** created."
*** 1892,1905 ****
        (append minibuffer-prompt-properties (list 'face 'minibuffer-prompt)))
  
  (defface region
!   '((((type tty) (class color))
       :background "blue" :foreground "white")
      (((type tty) (class mono))
       :inverse-video t)
-     (((class color) (background dark))
-      :background "blue3")
-     (((class color) (background light))
-      :background "lightgoldenrod2")
      (t :background "gray"))
    "Basic face for highlighting the region."
    :version "21.1"
--- 1894,1907 ----
        (append minibuffer-prompt-properties (list 'face 'minibuffer-prompt)))
  
  (defface region
!   '((((class color) (min-colors 88) (background dark))
!      :background "blue3")
!     (((class color) (min-colors 88) (background light))
!      :background "lightgoldenrod2")
!     (((class color) (min-colors 8))
       :background "blue" :foreground "white")
      (((type tty) (class mono))
       :inverse-video t)
      (t :background "gray"))
    "Basic face for highlighting the region."
    :version "21.1"
*************** created."
*** 1990,2013 ****
  
  
  (defface highlight
!   '((((type tty) (class color))
!      :background "green" :foreground "black")
!     (((class color) (background light))
       :background "darkseagreen2")
!     (((class color) (background dark))
       :background "darkolivegreen")
      (t :inverse-video t))
    "Basic face for highlighting."
    :group 'basic-faces)
  
  
  (defface secondary-selection
!   '((((type tty) (class color))
!      :background "cyan" :foreground "black")
!     (((class color) (background light))
       :background "yellow")
!     (((class color) (background dark))
       :background "SkyBlue4")
      (t :inverse-video t))
    "Basic face for displaying the secondary selection."
    :group 'basic-faces)
--- 1992,2015 ----
  
  
  (defface highlight
!   '((((class color) (min-colors 88) (background light))
       :background "darkseagreen2")
!     (((class color) (min-colors 88) (background dark))
       :background "darkolivegreen")
+     (((class color) (min-colors 8))
+      :background "green" :foreground "black")
      (t :inverse-video t))
    "Basic face for highlighting."
    :group 'basic-faces)
  
  
  (defface secondary-selection
!   '((((class color) (min-colors 88) (background light))
       :background "yellow")
!     (((class color) (min-colors 88) (background dark))
       :background "SkyBlue4")
+     (((class color) (min-colors 8))
+      :background "cyan" :foreground "black")
      (t :inverse-video t))
    "Basic face for displaying the secondary selection."
    :group 'basic-faces)
Index: lisp/custom.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/custom.el,v
retrieving revision 1.70
diff -c -3 -p -r1.70 custom.el
*** lisp/custom.el	29 Dec 2003 11:53:19 -0000	1.70
--- lisp/custom.el	12 Feb 2004 21:42:10 -0000
*************** following REQ are defined:
*** 306,311 ****
--- 306,315 ----
  `background' (what color is used for the background text)
    Should be one of `light' or `dark'.
  
+ `min-colors' (the minimum number of colors the frame should support)
+   Should be an integer, it is compared with the result of
+   `display-color-cells'.
+ 
  Read the section about customization in the Emacs Lisp manual for more
  information."
    ;; It is better not to use backquote in this file,
Index: lisp/font-lock.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/font-lock.el,v
retrieving revision 1.214
diff -c -3 -p -r1.214 font-lock.el
*** lisp/font-lock.el	26 Jan 2004 23:03:43 -0000	1.214
--- lisp/font-lock.el	12 Feb 2004 21:42:11 -0000
*************** Sets various variables using `font-lock-
*** 1560,1583 ****
  ;; But now we do it the custom way.  Note that `defface' will not overwrite any
  ;; faces declared above via `custom-declare-face'.
  (defface font-lock-comment-face
!   '((((type tty pc) (class color) (background light)) (:foreground "red"))
!     (((type tty pc) (class color) (background dark)) (:foreground "red1"))
!     (((class grayscale) (background light))
       (:foreground "DimGray" :weight bold :slant italic))
      (((class grayscale) (background dark))
       (:foreground "LightGray" :weight bold :slant italic))
!     (((class color) (background light)) (:foreground "Firebrick"))
!     (((class color) (background dark)) (:foreground "chocolate1"))
      (t (:weight bold :slant italic)))
    "Font Lock mode face used to highlight comments."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-string-face
!   '((((type tty) (class color)) (:foreground "green"))
!     (((class grayscale) (background light)) (:foreground "DimGray" :slant italic))
      (((class grayscale) (background dark)) (:foreground "LightGray" :slant italic))
!     (((class color) (background light)) (:foreground "RosyBrown"))
!     (((class color) (background dark)) (:foreground "LightSalmon"))
      (t (:slant italic)))
    "Font Lock mode face used to highlight strings."
    :group 'font-lock-highlighting-faces)
--- 1560,1587 ----
  ;; But now we do it the custom way.  Note that `defface' will not overwrite any
  ;; faces declared above via `custom-declare-face'.
  (defface font-lock-comment-face
!   '((((class grayscale) (background light))
       (:foreground "DimGray" :weight bold :slant italic))
      (((class grayscale) (background dark))
       (:foreground "LightGray" :weight bold :slant italic))
!     (((class color) (min-colors 88) (background light)) 
!      (:foreground "Firebrick"))
!     (((class color) (min-colors 88) (background dark)) 
!      (:foreground "chocolate1"))
!     (((class color) (min-colors 8) (background light)) 
!      (:foreground "red"))
!     (((class color) (min-colors 8) (background dark)) 
!      (:foreground "red1"))
      (t (:weight bold :slant italic)))
    "Font Lock mode face used to highlight comments."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-string-face
!   '((((class grayscale) (background light)) (:foreground "DimGray" :slant italic))
      (((class grayscale) (background dark)) (:foreground "LightGray" :slant italic))
!     (((class color) (min-colors 88) (background light)) (:foreground "RosyBrown"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "LightSalmon"))
!     (((class color) (min-colors 8)) (:foreground "green"))
      (t (:slant italic)))
    "Font Lock mode face used to highlight strings."
    :group 'font-lock-highlighting-faces)
*************** Sets various variables using `font-lock-
*** 1588,1658 ****
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-keyword-face
!   '((((type tty) (class color)) (:foreground "cyan" :weight bold))
!     (((class grayscale) (background light)) (:foreground "LightGray" :weight bold))
      (((class grayscale) (background dark)) (:foreground "DimGray" :weight bold))
!     (((class color) (background light)) (:foreground "Purple"))
!     (((class color) (background dark)) (:foreground "Cyan"))
      (t (:weight bold)))
    "Font Lock mode face used to highlight keywords."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-builtin-face
!   '((((type tty) (class color)) (:foreground "blue" :weight light))
!     (((class grayscale) (background light)) (:foreground "LightGray" :weight bold))
      (((class grayscale) (background dark)) (:foreground "DimGray" :weight bold))
!     (((class color) (background light)) (:foreground "Orchid"))
!     (((class color) (background dark)) (:foreground "LightSteelBlue"))
      (t (:weight bold)))
    "Font Lock mode face used to highlight builtins."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-function-name-face
!   '((((type tty) (class color)) (:foreground "blue" :weight bold))
!     (((class color) (background light)) (:foreground "Blue"))
!     (((class color) (background dark)) (:foreground "LightSkyBlue"))
      (t (:inverse-video t :weight bold)))
    "Font Lock mode face used to highlight function names."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-variable-name-face
!   '((((type tty) (class color)) (:foreground "yellow" :weight light))
!     (((class grayscale) (background light))
       (:foreground "Gray90" :weight bold :slant italic))
      (((class grayscale) (background dark))
       (:foreground "DimGray" :weight bold :slant italic))
!     (((class color) (background light)) (:foreground "DarkGoldenrod"))
!     (((class color) (background dark)) (:foreground "LightGoldenrod"))
      (t (:weight bold :slant italic)))
    "Font Lock mode face used to highlight variable names."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-type-face
!   '((((type tty) (class color)) (:foreground "green"))
!     (((class grayscale) (background light)) (:foreground "Gray90" :weight bold))
      (((class grayscale) (background dark)) (:foreground "DimGray" :weight bold))
!     (((class color) (background light)) (:foreground "ForestGreen"))
!     (((class color) (background dark)) (:foreground "PaleGreen"))
      (t (:weight bold :underline t)))
    "Font Lock mode face used to highlight type and classes."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-constant-face
!   '((((type tty) (class color)) (:foreground "magenta"))
!     (((class grayscale) (background light))
       (:foreground "LightGray" :weight bold :underline t))
      (((class grayscale) (background dark))
       (:foreground "Gray50" :weight bold :underline t))
!     (((class color) (background light)) (:foreground "CadetBlue"))
!     (((class color) (background dark)) (:foreground "Aquamarine"))
      (t (:weight bold :underline t)))
    "Font Lock mode face used to highlight constants and labels."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-warning-face
!   '((((type tty) (class color)) (:foreground "red"))
!     (((class color) (background light)) (:foreground "Red" :weight bold))
!     (((class color) (background dark)) (:foreground "Pink" :weight bold))
      (t (:inverse-video t :weight bold)))
    "Font Lock mode face used to highlight warnings."
    :group 'font-lock-highlighting-faces)
--- 1592,1662 ----
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-keyword-face
!   '((((class grayscale) (background light)) (:foreground "LightGray" :weight bold))
      (((class grayscale) (background dark)) (:foreground "DimGray" :weight bold))
!     (((class color) (min-colors 88) (background light)) (:foreground "Purple"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "Cyan"))
!     (((class color) (min-colors 8)) (:foreground "cyan" :weight bold))
      (t (:weight bold)))
    "Font Lock mode face used to highlight keywords."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-builtin-face
!   '((((class grayscale) (background light)) (:foreground "LightGray" :weight bold))
      (((class grayscale) (background dark)) (:foreground "DimGray" :weight bold))
!     (((class color) (min-colors 88) (background light)) (:foreground "Orchid"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "LightSteelBlue"))
!     (((class color) (min-colors 8)) (:foreground "blue" :weight bold))
      (t (:weight bold)))
    "Font Lock mode face used to highlight builtins."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-function-name-face
!   '((((class color) (min-colors 88) (background light)) (:foreground "Blue"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "LightSkyBlue"))
!     (((class color) (min-colors 8)) (:foreground "blue" :weight bold))
      (t (:inverse-video t :weight bold)))
    "Font Lock mode face used to highlight function names."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-variable-name-face
!   '((((class grayscale) (background light))
       (:foreground "Gray90" :weight bold :slant italic))
      (((class grayscale) (background dark))
       (:foreground "DimGray" :weight bold :slant italic))
!     (((class color) (min-colors 88) (background light)) (:foreground "DarkGoldenrod"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "LightGoldenrod"))
!     (((class color) (min-colors 8)) (:foreground "yellow" :weight light))
      (t (:weight bold :slant italic)))
    "Font Lock mode face used to highlight variable names."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-type-face
!   '((((class grayscale) (background light)) (:foreground "Gray90" :weight bold))
      (((class grayscale) (background dark)) (:foreground "DimGray" :weight bold))
!     (((class color) (min-colors 88) (background light)) (:foreground "ForestGreen"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "PaleGreen"))
!     (((class color) (min-colors 8)) (:foreground "green"))
      (t (:weight bold :underline t)))
    "Font Lock mode face used to highlight type and classes."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-constant-face
!   '((((class grayscale) (background light))
       (:foreground "LightGray" :weight bold :underline t))
      (((class grayscale) (background dark))
       (:foreground "Gray50" :weight bold :underline t))
!     (((class color) (min-colors 88) (background light)) (:foreground "CadetBlue"))
!     (((class color) (min-colors 88) (background dark)) (:foreground "Aquamarine"))
!     (((class color) (min-colors 8)) (:foreground "magenta"))
      (t (:weight bold :underline t)))
    "Font Lock mode face used to highlight constants and labels."
    :group 'font-lock-highlighting-faces)
  
  (defface font-lock-warning-face
!   '((((class color) (min-colors 88) (background light)) (:foreground "Red" :weight bold))
!     (((class color) (min-colors 88) (background dark)) (:foreground "Pink" :weight bold))
!     (((class color) (min-colors 8)) (:foreground "red"))
      (t (:inverse-video t :weight bold)))
    "Font Lock mode face used to highlight warnings."
    :group 'font-lock-highlighting-faces)
Index: lisp/isearch.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/isearch.el,v
retrieving revision 1.223
diff -c -3 -p -r1.223 isearch.el
*** lisp/isearch.el	1 Nov 2003 17:00:02 -0000	1.223
--- lisp/isearch.el	12 Feb 2004 21:42:11 -0000
*************** A value of nil means highlight all match
*** 2128,2153 ****
    :group 'isearch)
  
  (defface isearch
!   '((((type tty pc) (class color))
!      (:background "magenta4" :foreground "cyan1"))
!     (((class color) (background light))
       ;; The background must not be too dark, for that means
       ;; the character is hard to see when the cursor is there.
       (:background "magenta2" :foreground "lightskyblue1"))
!     (((class color) (background dark))
       (:background "palevioletred2" :foreground "brown4"))
      (t (:inverse-video t)))
    "Face for highlighting Isearch matches."
    :group 'isearch-faces)
  (defvar isearch 'isearch)
  
  (defface isearch-lazy-highlight-face
!   '((((type tty pc) (class color))
!      (:background "turquoise3"))
!     (((class color) (background light))
       (:background "paleturquoise"))
!     (((class color) (background dark))
       (:background "paleturquoise4"))
      (t (:underline t)))
    "Face for lazy highlighting of Isearch matches other than the current one."
    :group 'isearch-faces)
--- 2128,2153 ----
    :group 'isearch)
  
  (defface isearch
!   '((((class color) (min-colors 88) (background light))
       ;; The background must not be too dark, for that means
       ;; the character is hard to see when the cursor is there.
       (:background "magenta2" :foreground "lightskyblue1"))
!     (((class color) (min-colors 88) (background dark))
       (:background "palevioletred2" :foreground "brown4"))
+     (((class color) (min-colors 8))
+      (:background "magenta4" :foreground "cyan1"))
      (t (:inverse-video t)))
    "Face for highlighting Isearch matches."
    :group 'isearch-faces)
  (defvar isearch 'isearch)
  
  (defface isearch-lazy-highlight-face
!   '((((class color) (min-colors 88) (background light))
       (:background "paleturquoise"))
!     (((class color) (min-colors 88) (background dark))
       (:background "paleturquoise4"))
+     (((class color) (min-colors 8))
+      (:background "turquoise3"))
      (t (:underline t)))
    "Face for lazy highlighting of Isearch matches other than the current one."
    :group 'isearch-faces)
Index: lispref/display.texi
===================================================================
RCS file: /cvsroot/emacs/emacs/lispref/display.texi,v
retrieving revision 1.112
diff -c -3 -p -r1.112 display.texi
*** lispref/display.texi	6 Feb 2004 09:23:38 -0000	1.112
--- lispref/display.texi	12 Feb 2004 21:42:11 -0000
*************** What kinds of colors the frame supports-
*** 1613,1618 ****
--- 1613,1622 ----
  @item background
  The kind of background---either @code{light} or @code{dark}.
  
+ @item min-colors
+ An integer that represents the minimum number of colors the frame should
+ support, it is compared with the result of @code{display-color-cells}.
+ 
  @item supports
  Whether or not the frame can display the face attributes given in
  @var{value}@dots{} (@pxref{Face Attributes}).  See the documentation