Holly geezz Mark, the green and blue seem within reach of the Pearlex powders that I buy from the supplier in Adelaide but the red and grey, ain't going to be easy.
I know that Eugene, the fellow that makes the "Mutts" casting blanks, have the biggest selection of colours I've seen and according to a conversation I had with him, most colours are made to order for him...!
I also know that is a manufacturer in China that makes and sells almost any colour you can think of, the problem is the quantities needed to buy to get it in the first place, and unless you do really lots of castings, the investment on the powders, would be draining you dry of $'s...!
Lets see what other folks have to say...!
Cheers
George