I tinted my windows with car window tint film, I just went to the local car window tinting company (used yellow pages) and gave the counter clerk a couple of quid for off cuts, they where probably going in the bin. He gave me a choice of colours and varying degrees of window tint film, which is sticky one side, dead easy to apply provided you use soapy water on the window. You could buy tinted plasticard, from ebay or local model/hobby store.
I tried painting, but you get an uneven paint distribution, or brush marks with a brush, this turned out quite good, I just wanted enough tint to hide the electronics as I did not do cabin detail. The windscreen is done with the same film, its the darknes of the cabin that makes it look darker, Hope that helps