Primary Yellow of course! This Putty sits on my desk day after day. Gets pretty beat up from the amount of use. It has maintained it's color. I make fun shapes (Mostly inappropriate), it bounces, it tears into tiny little balls which I believe are what they consider the choking hazards and try to get thoughts from it but I think that is a lack of brain cells not the fault of the putty. It is a perfect gift for a co-worker. Thank you, Crazy Aaron!
One warning... Don't put it on your monitor and let it ooze down!
Disclaimer - I was not contacted by this company, this is a product that I have on my desk at work that I love.