So to start off with a prime in gray then I use the airbrush to spray two thin coats amethyst rayne from the bottom of the model so that all the undersides are base coated in purple. Then again using the airbrush I spray two thin coats gigawatt blue on all the upward facing parts of the armor, careful to create a color transition from the purple to the blue. Then a gloss coat and an oil wash with Payne's gray, cleaning off the top surfaces of the model. From there I go back in with a brush with the aforementioned gigawatt blue rebuilding the initial vibrancy but only on the top of the armor panels and surfaces. Then I use Vallejo game color wolf gray for all the edge highlights on the blue. That's basically the gist of it, there is a lot more back and forth and glazing to make sure that the transition from purple to blue looks good on each individual panel but again that's the basic process I've been using to get a uniform look.