Gotta disagree with Tre - Colors turn black with depth (red going fastest). Interestingly, black is the most visible color when viewed from below in the water(a fish's perspective).

As far as salmon biting in fresh water, I used to hike the Kalama in the fall and fish for smaller chinook that could pass through the weir. Technique was to position on the bank above deep slots and flyline small clumps of eggs with a couple of split shot. In undisturbed holes, the first few casts would always be met with aggressive hits. These fish were seeking out and eating these small clumps of eggs, not being lined or striking a kwickfish that was marching downstream at them out of defense.