A little theory to maybe justify the light fury

stormcutter:

What if there were no other night furies to begin with? They were always white and Toothless is the weird one out. Not being wanted when he was a baby being the ugly duckling with black scales and freaky green eyes. Being forced to leave his original habitat (hidden world), wandering around trying to find a place to belong, hunting in night to camuflage and being seen by a few people in many long years but leaving such a huge impact that they decided to call him the Night Fury. Until he finally met Hiccup, who was also the weird one out at the time, found what he was looking for and noone ever saw one again.