A short clip of "Rise of the Constructicons" is up on Youtube now. No sound but it doesn't matter since it's from a middle eastern channel so it's dubbed in Arabic.
http://www.youtube.com/watch?v=kPStoVWquHI
Some who have attended Botcon mentioned that Hasbro showed animation models of them in 2 colour schemes. Yellow and brown w/ yellow eyes and green and purple w/ red eyes and 'Con emblem so presumably they change colours when they go from neutral to 'Con.
Also, we've seen a pic of Scrapper's head from some time back where he's in green with red eyes and the cropped butt crack Mixmaster image was also in green/purple so I wouldn't worry too much about the colours.