Thats my thoughts as well. I have caught several pike, walleye and even a few perch that had different pigmentation based on the water they inhabit. Usually clarity and temperature of the water are the main cuplrits but as well bottom base or vegetation can also cause this slight colour variation. The meat or flesh colour can also be subject to change based on their diet. I have caught pike that are as pink as salmon based on the fresh shrimp diet, meanwhile others are almost yellowish/white based on all the silver bait fish they chum down on.