Well that's interesting Cecil. I have thought that when my water temps are colder, my trout a more colorful. I suppose when they die, they have all the warm blood in them, and usually the outside temps are warmer(part of the reason why they might die naturally), but apparantly the flesh/skin when froze still has the ability to change back. Neat...
Trout and most other fish are poikilothermic -- no warm blood -- they take on the temps of water they are in. Pretty sure water temp does not effect pigment. Diet and hormones have the biggest effects on the color of a fish. Light penetration and background colors do too.
