Flecked with every color of... you guessed it! A rainbow! Each feather is a different hue, and each shines with colorful light that spreads to every corner of your isle! It also has amazing eye shadow because it looks fabulous.
People believe pots of gold can be found by rainbows, but in the Dragon Realm, Rainbow Dragons flock to Gold! Miners and prospectors during the gold rush would often be puzzled by the random rainbows that would appear near their panhandles. Were they Rainbow Dragons in disguise? No one knows! But yes.
Rainbows in the human realm represent peace and love, probably because Rainbow Dragons are so cuddly and sweet. Rainbow Dragons make great companions; they've never met a caretaker they didn't like.
You'd best be a peaceful and loving person around an Epic Rainbow Dragon. Paragons of peace, these large and in charge dragons strive to make sure everyone is as happy as they are. Of course, they won't be violent toward you if you're not loving, but they will be particularly snarky.