Bristlenose Plec Colour Change

Does anyone know anything about why BN Plecs change colour?

The last couple of days I've been watching the fish and Bertie (the BN) in particular, feeding. I've noticed that he changes colour when he comes out of his hiding place, from dark brown to distinctly spotty. I can't decide if it's camouflage and because he's moving from the dark bogwood to the gravel, or because he's coming to get food.

Hi @Littlefish. I think I've had Bertie about 3-4 years. (My ability to keep track of time has completely disappeared since I had kids).

I don't think it is a (negative) stress response. Bertie is excellent at hiding - I never see him at water change, which I imagine is stressful for him. And he seems pretty happy at feeding time; comes out, potters around, doesn't dash off and hide. He is the biggest fish in my tank and seems to know it. He seems completely unphased by the kuhli loaches, the only other bottom feeders in my tank - if they're eating the wafer he wants, he just heads over, at his usual pace and they make way for him.

So from what you've said you read, I'd guess it is more likely to be a camouflage thing. It is quite a sudden change in colour.  He comes out of his hiding place in the bogwood dark brown, I blink and he's suddenly spotty all over. I have seen him with different markings as well, a bit like a saddle of spottiness. It is one of the things that makes him interesting to watch.