Red Pencil Urchins are easy to spot and are unmistakable when you see them. They are very red and their spines are quite wide. At night, their spines can turn a chalky pink. Back in the day, people used to use the spines of these guys as chalk on a chalkboard, hence the name red pencil. They need a lot of algae to live and they do not well in captivity. In Hawaii, they get up to 8 inches wide. Here on Johnston, I have seen them be 12 inches wide.
Johnston Atoll Adventures 
Why do they turn chalky pink at night?
Looks like a Christmas ornament to me.