Well, to say that any animal is "color-blind" is a rather misleading statement...early dissections theorized that since non
H.sapiens eyes don't have the same structure, of course the eye must be more primitive or lacking the ability to see in colour.
I can't say much about cephalopod eyes...I never dissected one (spent all my semester lab time on the muscle structure of
loligo beaks) , but I have found out that a lot of "accepted" truths are based in broo-hoo-ha.
I am sure one of our academics can put this issue to rest.
greg