Hi Pilou, I'm not actually sure what you are describing, because you mention both assigning a color randomly and at the same time you seem to be asking about assigning specific colors to types which then does not sound random to me.

There is a script that will randomize the colors of your styles though if that is of any help, that's available here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2987.2

- Michael