Seconding what others have said. Pick whatever colors you like, just make sure that the denomination is clearly legible, and that colors and edge spots are distinct enough that you can tell chips apart. The lighting in your room and the backdrop of your table can affect what colors are easy to distinguish, if you're under bright blue office lights you can probably tell anything apart, in a dimmer room colors will start to blur.
Except for Red. Reds are always 5. 5s don't have to be red, but reds have to be 5.