Photographer: Paul Osmond
(see this users gallery)
This is a Crinoid Squat Lobster, also known as an Elegant Squat Lobster (Allogalathea elegans).
As usual, the coloration of an individual is determined by the color or the crinoid feather star that it is found on. They are generally hard to photograph, spending the majority of their life deep inside the host crinoid.
Image taken on the on the Tulamben Slopes dive site in Tulamben Bay in Bali, Indonesia.