What the hell are colored memes?

In other questions, mattbrowne has mentioned the concept of variously colored memes. It sounds like a cool idea, but I don’t know what it means. So if any of you learned people out there could help me out, preferably with examples from your own life, I would be indebted to you.

Oh, and if you want to make a creative or funny answer, please feel free. I mean colored memes?