Coho salmon have silver sides and a deep blue back.
Chinook salmon also have silver sides, but their backs are blue-green with black spots. Chum salmon are greenish blue all over. Steelhead have blue backs with small black spots and silver sides, sort of like the coho Sockeye are greenish blue with smallish black flecks on their backs. Spawning males have pale green heads and bright red bodies. Most salmon turn reddish during spawning.