What colors do I use to make my buttercream a tan or mocha color?

i am thinking brown and a soft yellow or ivory? Just a guess so not sure so Bump! lol

Usually when I want a brown I use cocoa, but if you dont want chocolate flavor then just use brown paste just a little will give you tan, more brown and a dash of black will give a deep dark color, or if you use brown and a touch of golden yellow you'll get a camel"y" color. In my pics the swimsuits cookies I used just a tiny bit of brown in white ri for the skin color.

I agree... brown with a touch of yellow.