Litwick and Reshiram are the only cases I remember too; by the way, Reshiram being able to use blue fire was one of the things that made me love it. It's a shame that almost all Pokémon use standard yellow fire and electricity (I'm now thinking of Zekrom's shiny form; that green electricity looks so good, especially when combined to its dark color scheme).
I wish I could get both Charizardites in the same game. It's really hard to pick just one of the Mega Charizard.
In fact, it was a pretty sudden color change from Quilladin to Chesnaught. They should have put some of that light tan shade on Quilladin, so it would be a smoother transition. Like the Oshawott line: first white with some light blue, then light blue with some dark blue, then dark blue. I hope you're right about Delphox's robe, that helps the design for me. The image I saw made it look like a muddy brown, which definitely did not look good.
I agree that it fits their themes and I was bothered by that other part too — I know the mascots don't always have a fair relation when it comes to types (Kyogre and Groudon), but I do prefer when they're more equal. I hope they give Yveltal some Poison-type moves, I think it would fit (by the way, I would have liked that type for it, Dark/Poison... since it represents death, destruction and such, Poison would be fair enough). Talking about themes, I was wondering what the third legendary could be about.