We have two crimson/black and one black. My (older) crimson/black has the worst yellow cast to it. The newer crimson/black has absolutely no yellow tint at all. The newer black has a slight yellow cast, but not as bad as my older crimson/black. The two newer DS's were purchased at the same time. On the other hand, the black one has a noticeably superior viewing angle than both of the crimson black DS's.
So what's that all mean? Personally I think it means it's just a crap shoot and has nothing to do with the color of the DS. The crimson/black got a misguided bad rap. If you buy a DS, the quality of the screen will vary. That's it. The good news is that, with time, I find that it's just not that big of a deal either way. I love my DS, even though it has the yellow cast to it. Most of the time you don't notice it, and even when you do, it doesn't bother me any more. I should say, though, that at first I was pretty taken back by it and was considering returning it. I never did, though, and after while I got over it. So I say buy whatever color you like. You're just as likely to get a good screen as a less good screen. Nintendo probably buys whatever screens are available cheapest at the time of manufacture.