I believe everything you just said when it comes to countershading and that is all correct it doesn't matter what color a top water bait is. however when it comes to a sinking bait I believe a solid color will still give you a better advantage due to disruptive coloring which almost all fish have as a camouflage(the dots and stripes you see on fish) this acts to break up the predators prey image and allow the prey to escape while the predator is pondering whether the black dot on a shad is its eye or its eye is its eye. a solid colored bait would allow your target species to obtain a prey image quicker and have no doubt to whether it is a single fish or multiple fish due to stripes.