Yes, the blue walleye I caught years ago had no yellow in their colouring at all. I was a logger at the time and we had just pushed a new road within a quarter mile of a previously inaccessible small lake. After work another fellow and I portaged in with a canoe and you couldn't keep them off the line. We hauled in a bucket of dead minnows but we needed no bait at all. Just bare hooks. They were voracious, and very blue.

This one looked like a hybrid. Blue and yellow. It is otherwise just an unrelated genetic quirk.