Plasticine comes in different colours, as well if i'm short of a colour.i warm up the plasticine and put 2 and 2 together and i get a load of fun colours.
Anyway anyone can have there view,
Personally i use Newplast modeeling clay, and its great
In fact this is what the aardman team used for wallace and gromit i believe?? correct me if im wrong
anyway you can pick it up at any hobbycraft (which is where i get mine from.) or even ebay!