Here are some examples:
* Brown: Many monkeys, like the Rhesus macaque, are brown.
* Black: The Black-handed spider monkey and the Mandrill are examples of black monkeys.
* Gray: The Gray-cheeked mangabey and the Capuchin monkey are gray.
* Red: The Red-capped mangabey and the Proboscis monkey are red.
* Green: The Green monkey has a distinct green coat.
* White: The Golden snub-nosed monkey and the Silver leaf monkey are white or silver.
There are also many monkeys that are multi-colored with combinations of these colors, spots, stripes, and other patterns.
So, the answer to your question depends on which monkey you're talking about!