They only start blue, when you make a shot they go through BGYOR.Got the answer
I settled on blue because the Trooper mode arrows are blue and I was trying to match the cards to the modes (and I used green for Cyborg since red was already taken on 2MTM card).
However, traditionally lock shots are green (as they are on IMdn)
Personally I'd have preferred the Cyborg insert to be closer to a deep yellow (same as the power mode pyramid inserts), and then make the Mummy orange.
2MTM as red I agree with

Not a problem, I'll still have one.