[Scaevolus]

Yes, but how do you know the true color of a fish, seaweed, or sand? That's the unknown part!

[Udik]

> how do you know the true color of a fish, seaweed, or sand

I am pretty sure that in most cases those colours are well known.

[afwaller]

I, personally, have picked up sand, shells, even seaweed from the ocean, and lifted it out of the water and looked at it with my eyes. I have released this technique to the world, patent free.