Diamonds in the D-to-F range are considered “Colorless”; these stones are the most rare, and therefore the most valuable.
Diamonds in the G-to-H range are considered “Near Colorless” and can offer more “value” with regards to pricing.
Diamonds in the I-to-J range are defined by having “Noticeable Color”. This is definitely subjective, and stone-specific.
For most shapes, we consider J to be the cutoff before yellow is “too noticeable”. Some shapes are better at hiding color than others; for example the Round and Emerald camouflage color much better than a Cushion, Pear, or Oval would.
Note: Colored diamonds (other than yellow) are valued gemstones. These diamonds have a distinct color grading system from “white” diamonds.
The Cut is comprised of several measurements of a diamond’s proportions, arrangement and alignment of the facets, and quality of the polish, which all determine how the facets interact with light.