bug#6227: Color isearch regexp submatches differently

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 20 Sep 2020 09:41:59 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: lennart.borgman@gmail.com, 6227@debbugs.gnu.org
> 
> > >   (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 "magenta3" :foreground "lightskyblue1"))
> > 
> > I meant that these deffaces aren't complete -- they look like examples,
> > and the examples are taken from the isearch face.
> > 
> > There should be more of them, and they should be complete, and they
> > should have better names (isearch-group-1 etc perhaps).
> 
> FWIW, I use simple definitions like this one for the
> eight regexp-level faces, not bothering with multiple
> kinds of displays.  (Not saying that's what isearch.el
> should do.)
> 
> (defface isearchp-regexp-level-8 
>   '((((background dark)) (:background "#12EC00003F0E")) ; a very dark blue
>     (t (:background "#F6F5FFFFE1E1")))  ; a light yellow
>   "Face used to highlight subgroup level 8 of your search context.
> This highlighting is done during regexp searching whenever
> `isearchp-highlight-regexp-group-levels-flag' is non-nil."
>   :group 'isearch-plus :group 'faces)

That's not the same thing at all: your face definition will work with
any terminal (through the automatic color translation).