trick or treat
And have a happy Halloween
We're going a little out of order here with the trick&treats because you specifically said a colour anomaly would be a nice treat! And I currently have a lot of odd bois on offer.
So I present to you, the dressed down Atlantic white-sided dolphin. One of the first colour anomalies I ever noticed, and that sparked my interest in this topic.
It's a rather strange anomaly because it does not follow a set pattern. There's no specific shifting of one colour layer or the other, and while the facial markings are darker it is not truly melanistic. Everything is just a little... weird. Most notable the white/ochre marking on the flank that gives this species its name is gone, and the grey sides go down much lower towards the belly.
This funky anomaly is not excessively rare, I've at least seen it on multiple photos of multiple individuals. It can hide in plain sight; leaping amongst regular members of a pod it doesn't stand out as much as you'd think. A great photo of one such individual can be found here (warning, dead dolphin in the link).

















