I have a new Chrimson & Black model that I just bought in October.
In order to get the screen to turn yellow, I have to tilt the DS away from me at a 230 degree angle, this makes the game almost unplayble at that angle. As far looking straight on or holding it at an angle tilted toward me there is no yellowing whatsoever. Furthermore, if the DS is held at any angle which allows easy gameplay there is no color degradation.
Anytime an LCD screen is tilted in any direction there is generally some sort of color washout. Don't believe me tilt you computer monitor upwards and see what happens.
It should also be noted that the pictures shown in the links have a camera taking a picture at that same angle mentioned above. I set my DS on my desk and moved back, sure enough the yellowing showed up. Then I tried to play Zelda at that angle, the yellowing stayed there untill I had to move forward to see what I was doing in order to play the game. My moving forward had nothing to do with the yellowing but rather the odd angle which didn't allow easy viewing of the screen and thus made it more difficult to play.
