I've never said anything to anyone directly while fishing about their choice of gear, but good grief....yellow rain gear? I can't really even imagine using it while dragging plugs even though it probably wouldn't bother the guy/gal wearing it, I'm sure it would spook the fish that the bank fishermen are trying to catch.
I watched a guy with a shiny fluorescent hunting hat (baseball type) walk upriver towards my position from the opposite side. This occured on the Elwha earlier this year. The water was clear and I could watch the fish upriver of him spook as he approached. It was pretty interesting to watch. Every time he stopped to fish, the fish that had been laying in front of him had already moved upriver towards me. I thought about telling him to loose the hat, but didn't think I could manage it without being sarcastic, so I said nothing and just allowed him to bumble his way along.
I just got off the phone with a fishing buddy of mine who went fishing with another friend this morning. He said he and his pard walked into the first hole of the morning only to find a guy standing there with a YELLOW rain coat. Well, forget finding any fish laying in open water. I'm convinced they beeline for the heavy brush and stay buried for a good long time when they see that kind of dazzling display.