Not having any Revel colours I have really enjoyed mixing tiny amounts of Vallejo Air paints to get the colour I need, or in many cases prefer for small components. I know we have flexibility in this area but its more fun than I thought. Mixing Rust with Signal Blue and a touch of black to get a good engine component colour was great. I dont really want to buy paints I might not use again just for one job. But thankfully there is Modelshade which is quite superb at giving comparisons. And where some aren't really close enough I make a colour up. Even RAF stations must have run out of standard paint and improvised sometimes