What a cutie, where'd you get him? Also, bad news, I think you were duped like me! Looks like your lad is a delta tail or roundtail.
My little boy was special ordered by petland & was labeled by their supplier as a blue halfmoon... He's a white/pastel with blue/red & iridescence delta (I knew he wasn't a halfmoon in the store as, even though he wouldn't flare for us, I could see that he didn't have enough finnage to flare to a full 180*). Over the last week though he has gained a lot more colour; when I first saw him, he was white with a few coloured spots. When I went back to pick him up, he had some faint blue and red on his fins. Now, and each day I look at him, I notice that he is getting more and more colour on the fins (the body is still totally white with iridescence).
Again, gorgeous colouring on you boy!