AE CS6 / Changing (fading) the color of tiles in a mosaic from color A to color B

Hi there.

I have a pattern similar to a chess board and some of its b/w tiles (randomly picked during the animation) should change their color form A to B. This over a time of 3 sec. Because the area I wanna animate is going to have a lot more tiles then a chess board I would be glad if I could automate this somehow.

Similar to this stuff:

http://www.revostock.com/Motion-Backgrounds/154651/Mosaic-Blink-backgr ound-Tiles-Loop.htm

http://videohive.net/item/broadcast-twinkling-slant-cubes-pack-03/3319 545

Any suggestions?

All the best,

T