if you plan to kill'em at further distances, camo becomes less "needed". The closer you want them or expect them to get, the more important it is and the less natural cover that you have to blend into, the more camo becomes necessary.
I've had ranchers that have joined me for some calling and all they wore was their brown carhart coveralls, and we still killed coyotes, But we also weren't letting the coyotes get in our laps before shooting them.