Re: Face color changes

[Richard Stallman]

    Suppose you more-or-less like a particular color theme you come across, but
    you would like to try it a little lighter or darker or greener or with more
    contrast or with a couple of the colors swapped.

I am not sure what "a couple of the colors swapped" means.  However,
it occurs to me that Customize, when showing a color, could offer
other ways to specify the color other than by name.  It could offer a
menu of color operations, or run a color-specification dialog, or
whatever seems useful.