DIY colouring components
There are  Powder-Coating kits that are made for home use. They are available in the U.S. from Sears-Craftsman, The Eastwood Company and others. They range in price from under $200 to as much as you want to spend. The process involves using the supplied gun to apply a colored dry powder to the part. The part is then baked in a household oven. The baking cures the powder to something similar in appearance to a ceramic glaze. It is a very durable finish. It does create some issues though. It cannot be touched up if damaged. The coating is thicker than paint. Threaded holes and close tolerence mating surfaces must be protected during the process. Of course you could only color components that can have all their plastic parts removed.