Color refers to the presence or absence of a dull yellow or brown tint in white diamonds, specifically. This color never changes or fades over time.
A colorless or pure white diamond – which is ideal – allows for more light to pass through it than a colored diamond (This is different than a fancy colored diamond, which demonstrates a naturally vivid hue that is distinct from white-range diamonds.).A colorless diamond, known as D in the GIA grading system, emits more sparkle and fire than an H or an I-classified diamond, for example. It is extremely rare to find a truly colorless diamond. Therefore, the whiter the appearance, the greater the value.
Note: Fancy Color diamonds, which range in color from Blue to Green to bright Yellow and Pink, do not follow this rule and are actually more valuable for their color.