Three large supermarket chains are facing a lawsuit for selling farm-raised salmon with artificial chemicals that was not labeled as such.

Eight consumers are behind the unprecedented lawsuit, which charges Albertsons, Safeway and the Kroger Co. with “deception, unfair business practices, breach of warranty and negligent misrepresentation in the sale of farm-raised salmon”.

The consumers said they would not have purchased the salmon had they known about the chemical additives. Wild salmon eat creatures like shrimp and krill, which contain chemicals that make salmon pink. Since farm-raised fish do not eat a natural diet, their flesh would be gray if not for artificial additives.

The chemicals used to turn farm-raised fish pink–canthaxanthin and astaxanthin–are found in nature and are not harmful, according to an industry official. The salmon are turned pink to make them more marketable, since many consumers prefer fish with the traditional pink color.

Federal and state law requires that farm-raised salmon be labeled as such, however the grocery chains named in the suit allegedly failed to list the chemical additives on the label.

Further, there is “significant controversy” over the effects of canthaxanthin, as it has been associated with retinal damage in the human eye.