Taz and Marvin are both so cute!
I love gerbils, I had several pairs of them when I was a kid and recently had a pair of black ones named Chocolate and Brownie.

Here is a color chart to show all the different colors they come in now.
Gerbil Colors
I think the Siamese coloring is pretty, I think it is a rarer color, I have only seen one in that color.