Hue means its basic coloration. Tone is the term used to denote the lightness or darkness of the hue. There are 11 tones, 0 to 10, with 0 being colorless and 10 being the darkest. Saturation is the strength of a hue and is considered to be the most important factor in grading tanzanite by most gemological professionals. The lower levels, 1, 2 and 3 are of warm colors like red, orange or yellow, while level 5 is strong and level 6 is vivid or rather over-colored.