If you look at what people wear in the Middle East and North Africa, which contain multiple deserts, you find these commonalities:
Loose-fitting — This allows air-flow underneath, which allows sweating, which keeps you cool. Also, keeping layers of air in between the skin and the outer layer acts as insulation.
Color — It doesn't matter. Black is fine, because it produces a chimney effect that provides additional air flow.
Material — Cotton and linen encourage breathability, but polyester blends are also popular because they're more durable and easier to keep wrinkle-free.