I have our 3 DS Lites sitting in front of me. Two are crimson and black and one is Onyx. My Crimson & Black (C&B #1 below) was bought several months ago and the other two were bought several weeks prior Christmas.
YELLOW CAST:
Crimson & Black #1 (mine): the most yellow cast to the touchscreen.
Crimson & Black #2: no yellow cast at all. The best of the bunch in terms of yellow cast or lack thereof.
Onyx: definitely better than crimson & black #1, but still a slight yellowishness. You might not notice the yellow cast at all without a direct comparison. In fact, I hadn't until this direct comparison.
None of the DS's have any yellow cast at all to their top screens. The yellow cast issue is only with the touchscreens.
VIEWING ANGLE:
Crimson & Black #1 (mine): left/right viewing angle is very good. Top/bottom viewing angle is only fair
Crimson & Black #2: left/right viewing angle is very good. Top/bottom viewing angle is only fair
Onyx: it's tough to say for certain, but the left/right viewing angle may be ever so slightly worse than both of the C&B's, but still quite good. However, the top/bottom viewing angle is much better than both of the Crimson & Black models, and is very good.
All the displays appear to be of roughly equal brightness. It's a bit hard to be certain which is brighter, if any. It's not clear if serial numbers indicate when a particular DS was built, but curiously enough, C&B #1, with the worst yellowishness, has the highest serial number.
So what does this all mean? I think the yellow cast issue seems to be a crapshoot. You could buy a Crimson and Black and get no yellow cast at all and you could buy an Onyx and get the yellow cast. Or vice versa. On the other hand, our Onyx DS clearly seems to have a different top and bottom screen, one that has a significantly better vertical viewing angle. It could be that the Onyx DS, having the lowest serial number, may be from an older build and they may have used a better screen at that time (from a vertical viewing angle standpoint). Or it could be that the Crimson and Black models are built in a different factory and they use a different screen, and the date of build may have nothing to do with it. They might also switch the screens they use again. I guess others will find out.
I'm considering now, having been able to do this direct comparison, returning my DS (C&B #1) for return/exchange with the hope of at least getting a less yellow screen and maybe getting lucky and getting a better vertical viewing angle. Then again, living without my DS for any length of time sounds painful, and really the yellow cast and even the viewing angle isn't *that* big of a deal. Hmm.