Age, water color, temperature, stress, and other factors affect the color of most fish. Bluegill, and pretty much all of the sunfish family, can really change over very short periods of time.
Recently, Bob Lusk arranged for the Pond Boss Moderators to have the great opportunity to visit a spectacular lake that he and his crew manage in Oklahoma on a 6800 acre property called
Wildcat Spring Ranch.
Several of us decided to spend our day electro-shocking the main lake on this beautiful property.
I'd never before done shocking. I was't surprised at what was shocked up. Instead, I was amazed at what the shocking did to the colors of the fish between the short period between when they were first shocked and when they returned from their comatose state in
a big livewell, where they were again full of life.
With more than 65 years of identifying freshwater fish, I had to ask about one of the types of fish we were shocking and bringing in for observation. Within a few minutes of putting these fish in the livewell, it was quite obvious they were big black crappie (12-14 inch). They had very few markings, and looked like they had just been pulled from a pail of Clorox water when we first pulled them after being shocked.
On that same lake we pulled in largemouth bass (LMB) coming up with red eyes very similar to of our eastern populations of Appalachian river system Small Mouth Bass ("brownbacks"). Within several minutes of being revived in the live tank, these LMB looked like regular LMB. They were a mix of Florida strain and plain old regular northern strain LMB.
Growing up way-north, I pulled thousands of fish from extremely cold water through small holes in the ice to find that they were all very bland in color.
Color is only one of several methods of identifying fish.