nancy, not a clue of what it could be, I've seriously haven't encountered/noticed this as I use coral sand lol.
Could you give us more detail's as i'm very curious about this, did he do it once you first introduced the deep blue color?
I've introduced the color to Ollie in a number of ways and first attributed his not liking deep blue things to the item - but they add up. For instance, I gave him a little clear glass bottle with a cork in it. He loves it and sleeps holding it. Then I tried to give him a similar bottle that was dark blue - he wouldn't take it. The same thing happened with a dark blue bioball. We've frightened him wearing dark blue clothing. I don't really want to continue the experiments, because they make him unhappy.
Ollie sees things outside the tank and reacts to them. I've started experimenting with colors that I wear when playing with him. Today I wore purple, and Ollie turned from orange to the very same shade of purple I was wearing (not his usual shade).
There were reports last year from a vulgaris owner that his vulgaris had an aversion to yellow!
oh dear, that must have been a very awkward adjustment for the owner.
Seem's to me that the color blue remind's him of something bad or harmful, as their natural instinct they try to identify predator's and the sort, maybe he feel's threatened by it for some reason, this is highly peculiar, very strange indeed!
It might be wise not to conduct any more experiment's, don't want him feeling threatened by his own owner, I wonder if ceph's can get seizures,hehe. :P
So how do octopuses match colors like red purple and blue purple? (my bimac specializes in lavenders and purples when he's relaxing at the mouth of his cave - there is coralline algae near him in various shades of purple) Do these colors have different polarity?