Elements in Nophra are more fluid than what would typically come to mind. There is a solid list of core elements (Water, Fire, Earth, Air, Light and Dark) but their potential sub-elements are infinite. If you can think it up, it exists.

There isn't a hard limit as to what color a Crystali's essence will be in relation to their magic. As long as it can be somewhat identifiable at a glance. The only real restrictions when it comes to essence color is that black or white essence is reserved for dark and light elements.

Light elements and magic are always linked to healing or life bringing.

Dark elements and magic are always linked to death, curses and diseases.