What Color is Your Salmon?
Farm-raised Salmon aren't salmon colored unless they're fed shrimp and krill like wild salmon (unlikely) or given artificial colors in their feed, such as Astaxanthin, a carotenoid marketed by Hoffman-LaRoche. Market research indicates that consumers associate darker pink colors with "better quality and better taste." (That's market research, not taste testing. Subjects were asked to LOOK at some fillets and state their preferences.)
In order to assist farmers in regulating the amount of pigment fed to their salmon, Hoffman-LaRoche sells the "SalmoFan" which can be held up to fresh salmon flesh to determine its coloration along a progression of values and then correlate how much Astaxanthin is needed to get the fish to the right color.
For photographs and discussion of the "SalmoFan," exuberently declared a "future classic of design" by no less an authority than Edward Tufte, see The Ask E.T. Forum at edwardtufte.com
Update: Mr. Tufte reports recently that carotenoids are also used extensively in zoos to keep the flamingos pink.