Uh...Need Advice

I have noticed on different planes that I have downloaded...some (like Mike Stones great aircraft) feature simple "monotone" paint schemes. With other planes (Team FS KBT F-18), once zoomed in, its not all one colour. There are different bits of greys splashed all over the place, giving it a nice photogenic effect. I was wandering, how exactly do you produce an effect similar to this?