GIA has made eight distinct color saturation grades for pink diamonds:

Very Light - Light - Fancy Light - Fancy - Intense - Deep - Dark - Vivid

Additionally there are various color combinations that must be accounted for including; Purplish-Pink, Orangy Pink and Brownish Pink.

The more pure the color of the stone, generally the more desirable and rare the stone. However, a modifying color such as purple is still considered quite desirable and is often seen favorably as opposed to a brown modifier which would reduce the value of the stone