Red skin for nautolans.

i know they are ocean based lifeform but still. i want my evil nautolan.

Re: ocean-based lifeform and redness.

I give you Lutjanus campechanus, the Northern Red Snapper, so-called because it is, well, red. It's an oceanic fish.

https://en.wikipedia.org/wiki/Northern_red_snapper

For e.g. squid and octopuses(1), "what colour is it?" is a largely meaningless question since they are able to change their colour, but some species do turn red in certain circumstances, sufficiently so that they are named for it.

(1) "Octopi" is wrong because "octopus" is derived from Ancient Greek, not Latin, so the etymologically correct plural would be "octopodes". It is, however, far more common to call them "octopuses" in modern English.

Language can be funny.

Cattle is plural. There is no word in the English language for one animal of this type. People will often say cow but that's wrong,

Cow is adult female.
Bull is intact adult male.
Calf is young one of either gender

A cattle rancher will correct you if you call his bull a cow.

It's vastly archaic, but the word you're thinking of is "neat". https://en.wiktionary.org/wiki/neat#Etymology_2

See also sense 2 of "ox" at https://en.wiktionary.org/wiki/ox