Which is the best dragon colour?

Well, it depends on the personality and powers of the dragon.

Tricky really. I guess it kind of depends on the dragon...but when drawing them in particular, I have to say I do like traditional green или red, but also black или gunmetal grey...though mind you, I drew one recently with royal python-patterned scales XD

I'd say white, as it is the colour of light and healing.