Michelle,
You need a .MSK file. It's basically a BMP file saved with a different extension. Edit TheImage.bmp with imagedit, color it all black save it as TheImage.msk in the same folder as the bmp and it'll look just like you used color safe bleach.
>Why is it that when I put a bitmap on a button, wherever that bitmap has white, it shows up grey? Is there some way to fix this? The only thing I could figure out is to change the white to the faintest yellow. Then the right colour shows up, but I'd rather have it white than yellow tinged.