I have to say I find the Genesis transaction mechanism quite awkward. Why not put the color definition (the URL encoded string) as a message in the transaction?

Also, the fact that you have to send coins to the COLGEN address is a no-no to me. This is an unnecessary dependency.

If you want adoption, colored coins need to be completely decentralized, as is Bitcoin. The "standard" shouldn't rely on a central address like COLGEN.