I routinely fish small mountain creeks for small wild trout in the mountains of western NC and eastern TN. These spring-fed creeks often run gin-clear and low. The small brookies that inhabit these streams are spooky. Very spooky. Fishing these small streams is often more akin to hunting than fishing. Keeping a low profile, sneaking/stalking a run is a necessity for success on a regular basis. When fishing these streams, I wear drab clothing (sometimes even camo), use any available cover to sneak within casting range (which is usually a short roll cast or a bow-n-arrow cast) and avoid shiny equipment if possible. I think that a bright, shiny reel "could" be a hindrance on such streams. One could argue that if they see the shiny reel, they are gonna see me too. That might be possible, but if I have a choice, I'm gonna choose a matte or dark colored reel for my small-stream trout rig every time. I need all the little advantages I can get! All my small-stream outfits are equiped with a dark colored reel.
If I'm on a larger body of water, I dont think the reel color makes much, if any, difference. My river smallmouth bass rigs have smoke-finish reels and I havent seen any problems. I've fished larger tailwater rivers for trout with glossy reels with really no problems. I just prefer to try to use every advantage on small streams I can due to the close proximity to the fish and clear, low water and spooky fish.