Rabbitfishes are really nervous and high-strung creatures. That can make working in the tank an adventure, when they freak out and swim quickly and erratically around the tank, considering that their dorsal spines are venomous :-/
We always called it 'ripe banana peel' when they went into stress mode and displayed that blotchy effect.
New acquisitions can remain in banana peel mode for up to a week or so until they start to feel comfortable in their new surroundings, and they can flip from 'normal' to 'banana peel freak-out mode' in a second.
Just be really slow and deliberate when you have hands in the tank, and always be aware of where the fish is and give it space. If it starts freaking out and swimming fast in every direction, get out of there. More people are tagged when the fish freaks out because it hits them by accident.
And IF you're tagged, run the wound under the hottest water you can stand, to break down the venom, and be ready to feel the burn for a while (and seek medical attention if in doubt.)
Jenn