I think if you manage to get the edited files the exact same size (shouldn't be hard if it's merely a color change) it should be fine. The patcher might look at the "Last edited" date as well, but that's easily fixed too.
Mind you, I really have no real clue so I might be talking outta my butt, but it seems to me there are really only so many ways the patcher can determine if a graphics file is out of date. Unless they have some fancy watermark deal going which I doubt.
Anyway, don't hold me to it, as it were...
