* Base: White is your primary ingredient. You'll need a lot of it.
* Mix with:
* Brown and Yellow
* Tan and White
* Yellow and Gray
* or even tiny amounts of Black, Blue, and Yellow
Key is to add small amounts and mix thoroughly until you reach the desired shade. It's easier to darken a color than to lighten it.
Tips:
* The specific shade of brown, yellow, or gray you use will affect the final beige color. Experiment to find the combination you like best.
* Use a palette knife or similar tool for mixing to avoid contaminating your paints.
* Mix more paint than you think you'll need to avoid running out and having to rematch the color later.
Good luck!