Most of this is handwaving. The color of the fish has nothing to do with it's health; it comes from certain materials in the diet. Moreover, farmed salmon has lower prevalence of parasites: https://munchies.vice.com/en_us/article/d755kx/almost-every-...
The farmed salmon require constant medication to combat the parasites that thrive in dense populations of confined salmon. The wild salmon, however, do not benefit from the medication, but do pick up the parasites as they swim past open-net salmon farms. This is one of the many reasons why Pacific commercial fishermen are opposed to open net salmon farming specifically, rather than just to salmon farming in general; it is not just competition, it is literally destroying a species we depend on, and the ecosystems that depend on them in turn.
Sorry about the lack of a citation, I found out about this while handling tons of infested salmon over several summers, not by reading a study. Last I heard, a study was commissioned by the DFO, but the results were kept private by the BC government; communications by government sponsored scientists were tightly regulated, beginning during premier Gordon Campbell's time in office.
