I actually have 3 chaos teams but only one with a mino painted to suit the team. There is a pic posted somewhere here abouts. Here's the link
http://www.talkbloodbowl.com/phpBB2/vie ... 91&start=0
It's not the new one though, rather a conversion. I want the new one as well but i rarely field minos so really have no need. Anyway as to color, i think it depends on what sort of team you plan on playing. If i were making a Nurgleish team, the mino would be greys and whites. The one i made is for Slaneesh so i gave him more of a fleshy color tone. Chaos undivided i would go with a very dark brown.
For Khorne i think a redish hue would work, ya know a nice dark brown with a barn red highlight.