2 shade (or n shade) hardware blit

[mute]

How difficult would it be to blit to multiple surfaces (overlay colors) with different brightness? I already use blit mode with almost every surface (barring text and absolutely necessary highlights/shadows) set to the overlay color. I've tried setting my editor's background to the overlay color, but bright effects wash out the text at times. If it's possible, it'd be very cool to have a second overlay color that gets filled with darker values of the colors, sorta giving a translucent appearance to the body of the editor window.

In fact, if you could get 3 layers, you could even set up the windows hilite/shadow colors as lighter/darker overlays of the effect.

Is this stuff possible?