> See attachments.
>
> The idea is to use less contrast for the pilcrow.  The whitespace.el 
> colors do the exact opposite: they emphasize the whitespace over the 
> normal text, which is great if and only if you want to just check 
> whitespace and then turn it off again.


Hmmm, yes, it looks good, but lightgrey is a problem with dark 
background and a white foreground, as lightgrey and white have low contrast.

I made some tests with the following setting:

(defface whitespace-newline
  '((((class color) (background dark))
     (:background "grey22" :foreground "gray" :bold nil))
    (((class color) (background light))
     (:background "floralwhite" :foreground "gray" :bold nil))
    (t (:bold nil :underline t)))
  "Face used to visualize NEWLINE char mapping.

See `whitespace-display-mappings'."
  :group 'whitespace)

See the attached images.