@Devil May Cary You have a point. However, being the embodiment of all things nature, I'd suspect she can change her appearance somewhat. I'd say that she uses those colours just because she can, and they look really awesome. But you'll have to ask @2964artworld to get the real reason.
You are correct in saying that those colours are rare in nature and also that more earthy colours would be good to use. I'd say that she would probably have been born looking different to how she looks now. She has just changed those colours and now prefers to look like the rarest colours in nature to show off. Also if I'm not mistaken, her father is blue and white so...