The PSP wasn't beating the DS every week, they were more even (although the PSP was winning a bit more). Agreed that it was Nintendogs that really pushed the DS ahead.
As for multiple system colors, I don't see it happening anytime soon. They are having a hard enough time manufacturing enough systems in just 1 color. Same thing with Wii Remotes and Nunchuks, Nintendo sells a sh*t-ton of both. If/when sales slow down (it's been over 2 years and they are still selling tons of systems here in the US and a good amount elsewhere), then maybe they will.