This is a fascinating thread, and I share a few of the same concerns. The screencap of the King's dream is very disturbing to me, and I didn't even realize the change until you posted it. The situation with the whites turning into blues was something I noticed, but didn't bother me. I think it's some sort of artistic choice that wasn't visible in the old trasnfer. Notice how only the antagonists have blue eyeballs. I think it's to render them more cold and less approachable.
Disney Duster listed one of my concerns, though: when Cinderella first enters the palace, her dress is pale blue, and her hair is an almost blazing yellow. Now, the dress thing I would normally shrug off because there ARE shots where it's blue because it's reflecting shadows and the night sky. When I compared that shot to the old transfer, though, the gown was flat-out silver, and her hair was reddish brown. I can understand hues changing slightly because the old version would've been a darker, more deteriorated representation of what was originally painted...but silver turning into blue and tawney turning into orangey yellow? That's a bit too drastic of a change. Observe (sorry for the quality of the pic; the left hand one was taken from a Quicktime file of the DVD trailer while the right hand one was taken from a WMV file of the music video before the DVD was released):
A similar thing happens in the "Dream Is A Wish Your Heart Makes" sequence. Cindy's hair (which can be seen in my signature) is too orangey yellow compared to the old transfer where, again, it's a reddish brown tawney. Heck, forget the old transfer. Cindy's hair in this scene is yellower than every other scene on the DVD (with the exception of the palace entrance shot above). Something's not quite right there. Unfortunately, the Cinderella galleries on the DVD show no color keys for the characters like Sleeping Beauty's does, so we have no direct reference point to compare besides the old transfer. I normally trust Lowry Digital (the team behind this) with these transfers because they've stated time and time again that they refer back to the original hand-painted cels as reference points. All of their other Disney transfers (Snow White, Bambi, Alice in Wonderland, Lady and the Tramp, and Sleeping Beauty) lead me to believe that they do, indeed, do that. Cinderella is the one that kind of makes me scratch my head.
If pigs fly and I ever have a chance to explore the Disney Vault, one of the first things I'll do is check out the original Cinderella cels in storage and take pictures of them to compare.
As for Beauty and the Beast, that transfer I'm sure was a direct overhaul. NONE of the stills from my "Art of Animation: From Mickey Mouse to Beauty and the Beast" book look even remotely close to the DVD transfer. Since this book was published right when the film was released, this is certainly not a case of using aging photos. The only reason why I don't protest that transfer is because the filmmakers approved it, so they must want it to look that way.