Hes not a dragon. Very lovely with a gorgeous green iridescence to him, but hes just a Multi-color. ;)
The 'Dragon-Scale Crowntails' they've been selling at Petsmart aren't really dragons....or at least, I think I've only ever seen maybe one or two that was a true dragon. Most of the time they're metallic or iridescent or copper, but not dragon. ;)
Dragons have a very 'thick' looking metallic coloration meant to look like a dragons thick scale armor on just their body, stopping off at where their fins begin and usually with at least a partial mask(meaning the scaling is on at least part of their head). A plain metallic can look similar, but its still different....and a fish with an iridescence, like your guy, usually just looks sort of 'shiny' and often looks a little different from different angles depending on how the light catches it.
This offers a pretty good basic color guide: http://www.bettafish.com/showthread.php?t=29868
It can definitely be difficult to tell sometimes of course though, telling apart the different coloration and patterns is just something you learn over time with experience and looking at a LOT of fish. xD