Any of the browns on the light half of the spectrum, all the way down to London Tan. Every maker has different names for these colors, but for EG, say, Chestnut and lighter. A brown with a little red in it is also good. I would not hesitate to wear spectators (brown & white only, not black & white) with a tan suit, but I would not wear solid white. Another option is a leather & canvas spec, in brown and tan or brown and olive.