Now, I may not understand everything to due with themes, but wouldn't
it be relatively easy to create themes that allow the user to change the
color scheme? The theme author would simply define a set number of
"colors" (with default RGB values) and name them something like
"WINDOW_BORDER_GRADIENT_A" and "WINDOW_BORDER_GRADIENT_B" and then if
you want your window border to fade from blue to blank instead of red to
black, you would simply edit the RGB values of the colors on a nice GUI
form, part of the Gnome theme manager. A side effect of this may be
that graphics created for themes should be grayscale? Just some
thoughts... let me know what you think.