bug#9402: list-colors-display

[Juri Linkov]

> Aha, and what would your "system defaults" do when the background mode
> changes?  The Windows "default" region color is a very deep blue
> background, which will be almost invisible on a dark background.

Exactly the same deep blue background is currently used by default
on a dark background in the face definition:

  (defface region
    '((((class color) (min-colors 88) (background dark))
       :background "blue3")

:-P