I think special colors, flash and hotspots work well on stocked fish, for two reasons.
1. Their size is often incongruous with the biomass of the river, so they will eat anything and there is more emphasis on getting their attention.
2. They are less intelligent.
In contrast, I find that those things work poorly on wild fish, for the opposite reasons. There are always exceptions, though. For example, a period of unfavorable conditions might make a wild trout behave the same way.
FWIW, I once went down the rabbit hole of color theories and asked Devin Olsen for his thoughts on my findings. He said that he doesn't think about those sorts of things anymore, because there are too many variables and they rarely translate into results. He concluded that fly design is more of an art than a science. He encouraged me to find patterns that work and develop a rotation, rather than try to figure out why the patterns work.