So there are some "blue" clowns. I saw this same one and went Google diving. The current ones are not fully blue, they have bits around the head of I remember right. Still look pretty cool!
Pretty sure the photos are just a regular orange clownfish, but photo colors are inverted (orange becomes blue, black to white, white to black).
...and obviously the listing is an April Fools joke for the various reasons pointed out above.