and some other command to copy it back to the backbuffer
Sounds like a useful command. The saturation thing, you can't really do saturation or hue changes using RGB data, you have to convert the color space.
Can we draw a texture and tell gl to replace a certain color? Is that something a shader could do?Shaders are a newer thing right? Will they work in the current max wrapper for OpenGL? (v1.1?)
Do shaders require a newer graphics card?
P.S. To anyone about to post "go Google it," I have been, and even if I can find something it's specifically for 3D or has a bunch of other stuff going on, making it very hard to find what I'm looking for (referring to code.) I find it better to ask here.. just hardly any responses :(