walleye colors?

What do you suppose causes the vast color difference in the walleyes and saugers in the river?
Example, yesterday morning, while fishing P2, I had 2-18″ and one 15″ walleyes come to the boat that were all a beautiful dark-green and gold color. Then, in the same stretch of river, I had a downright ugly almost all white 26″ eye come in. What gives?
I’ve noticed this in P2, P3, and P4 over the years – from March to December, so it does not appear to be pool specific or a time specific condition. It also does not appear to be a small versus a large fish condition either. …They all seem to be healthy too.
The eyes from the lake that I predominantly fish on are all the same color, so I finally just had to ask…. Anyone know why the colors vary so much there?
Splitshot

Age of the fish and where they hang out I would suspect has something to do with it. My guess would be fish that hang deeper are more pale in color.