short spined urchin changing color?

[NBACHER]

12 days ago, I picked up a short spined black/brownish urchin. He hides during the day and comes out at night to graze on the algea in the tank. Last couple of days I noticed the tips of his spines are turning purple and the rest of the spines are now yellow.

Everything else in the tank is doing fine and seems to be healthy. I tested the water and everything seems normal. The urchin looks amazing now, but worried it has health issue.

 

[AmberFL03]

I saw a small urchin at my lfs with purple tipped spines...I thought it was pretty cool. I wonder if that's just the coloring?

 

[NBACHER]

I talked to guys at LFS and they always seem to be on point. They told me since it is under better lighting that it changes color. Compared it to a sun tan. Not a hundred percent on that but he seems happy and glad I got a great deal on a awesome urchin.

 

[Oceanminded]

Just found this thread doing a search, my urchin seems to be undergoing the opposite transformation. He started out with purple and yellow banded spines with a white body, now at day 2 in my tank his body seems to be getting darker in stripes. Water levels are fine and he's still acting like a happy little guy, wandering around eating algae with his menagerie of shells/small rocks.