Do they scare you when you see them? In and of themselves, flashes of color don't have any significance IMO. I often have flash visions not only of color but all kinds of pictures when I close my eyes and disconnect from thinking. It's not disturbing to me at all. Actually, I rather enjoy it because images are kind of pretty..To me it's no different from a dream.

But if your mind connects those color flashes to some disturbing thoughts or memories, then it's worth to look into.