Fishing many different streams in Northern Michigan, you can catch a brown in one creek or river, drive 3 miles to a different creek, and the browns in that creek look entirely different (shape, color, markings, etc.)
I believe there are many different strains/species of brown trout. I believe that many different species change with their environment and diet.
Same scenario as mentioned above:
I took a friend of mine trout fishing for the very first time. I did not want to frustrate this friend of mine with a fly rod his first time out, so I took him "Tube dunking" - as we call it around here (worm, barbless hook, no weight, toss it in the river or creek on the upstream side, and let it drift under the road through the tube. Click the bail shut, wait 3 or 4 seconds, then reel in slowly until you feel the fish). I wanted him to just feel the electric shock shoot up his arm and into his heart as he felt his first trout. I had been trying to get this person to go trout fishing for years.
The first fish my friend caught was vibrant in color, many spots, slim and slender body size, although the fish was a nice 14 inches long. The creek he caught it in was crystal clear and ice cold. The second fish he caught was a smaller creek 3 miles down the road. The creek was a little darker in color with a marrow bottom. I had the hardest time convincing him to float his worm through the little 14" diameter tube. He thought there was no way a fish would be hiding inside that tube inside this little, muddy, tiny creek.
The fish he pulled out of the tube took 5 minutes to land, and was approx. 21 inches long. The brown trout was brown almost black in color. The spots were a different color and barely recognizable (hardly any red spots at all) The fish was blocky / chunky in body size, it almost looked like a different species of trout altogether.
I have noticed many different creeks/rivers that the fish look a little different from place to place from Tennessee to Michigan.
I'll see you down on the river...