The color "pink", in a steelhead eyes may not be the same color that you or I see as the color "pink" as. It may just be a shade of gray, or some other color that they recognize as a food source or it could just be a color that really pisses them off.

Remember, a steelheads brain is only the size of a "pee", so the amount of pain that they may feel is most likely very limited. Why do you jump sometimes when someone makes a noise or grabs you from behind when you are not ready for it? You don't feel any "pain", but you still "jump" don't you?

If pain was a big factor, why would they (steelhead and salmon) let bears, or seals grab them and bite them and yet they just keep on going until they get to wherever their headed?

I don't believe that cold blooded creatures have the same nervous system as a warm blooded creature does, and that may also have an additional effect on how much pain they can feel.

Cowlitzfisherman