Weird solid color artifacts

[rubah]

Can anyone tell me what causes this behavior?
http://www.snowy-day.net/stuff/others/misbehaving-colors.png

As you can see, what should have selected an entire block of EoFF color has only selected a portion, and furthermore, there are three individual colors in use:
#003653
#003755
#003654

I had originally thought this to be a problem with OSX, but I'm told it happens on Windows as well. It's making it quite difficult to mock up screenshots for layout ideas :p

[Rantz]

I'm unsure, but I think clipboard handling of images might be at fault here, in much the same way copy-pasting images with transparency often causes the transparency to go lost (this could just be a Win/BMP problem though).

[rubah]

Huh, you might have something there. When I saved the screenshot directly from this page, I didn't see that behavior. That's so weird.

[Baloki]

I have the PSD file of the current EoFF layout xD