I don't mean to speak for anyone else, but I have "mixed" alclad on the model. Simply apply very thin "mist coats" until the color you wish is acheived. In other words, let's say you want dark aluminum, but not has dark as the parent color. Just shoot the panel with a dust coat of the darker color and then reload with polished aluminum or chrome and make a light pass until you are happy. The brighter color let's the darker come through creating a metallic contrast.
Steve