by DoomTurtle
I read through the rules, and the purple dice are optional. None of the cards reference it.However, you should note that the purple dice really aren't adding anything new. You simply choose to use them as a red, yellow, or white die and can combine them with others of the same type you choose it to be. It just acts a free die you get to roll in addition to the rest, and is purple so that you know it can't be bought by anyone else.