Here's my Chaos Underworld team all painted up, lining up against my human team. You can really see the size different from the large humans down to the little rats and goblins. The troll makes that even more apparent. Overall, I did the same base style as the humans, with white fatigues under the armour to bring home the football imagery. The models were all basecoated with wych flesh and skull white. The yellow was so easy, just one coat of Casandora Yellow. I drybrushed them after with white, and then used lamentor's yellow glaze; however I don't think those last 2 steps were needed if you're in a rush.
The goblins are camo green, which just looks very "gobliny" to me. I ultimately just wanted a light green since I plan to do orcs as well, and wanted them to be a mid tone, with darker orks as the Black Orcs. Basically the bigger and meaner, the darker the orc. The troll on the other other hand I wanted to stand out, and I just always think of blue trolls (from so much world of warcraft).
So many goblins to eat!
For the tokens, I used 1 from each of the goblin and skaven sets.
Just a minor change, by adding the khorne head crest. Also all of the rats had their tails cropped so they didn't break later or interfere with game play.