My brother and I were shopping together the other day (a rarity) and I pointed out to him that the wild salmon was much deeper in color than the farmed, but now that I think about it I don't remember any notice of any coloring. Which is unfortunate, since I already have trust issues with their fish.
One thing that my brother's family has bought from Sam's Club is salmon in a foil wrapper topped with compound butter. Just stick it in the oven, and as far as I know the consumer doesn't really get a good look at the color. Honestly, that could be a solution to grey fish, just sell it ready-to-bake.