Diamonds that are naturally colored are distinct from white diamonds, while being highly priced for their rarity and beauty. Colored diamonds not only find definition based on their color, but also their intensity. This can range anywhere faint to fancy deep.
This property does not elicit much consideration when it comes to colored diamonds. However, it is still important, as they do not have obvious inclusions or marks. The choice of shape is most affected by how intense the color should appear. You can have cases where a certain shape will make the color all but disappear, which is not what anyone wants in a colored stone.
No diamond is as rare as a red diamond, and very few of these get certified by GIA. The red color found in these stones results from a lattice distortion. The likelihood of modifiers being present alongside is very high, so what you usually get is a brownish red, pinkish red, purplish red, etc. The most coveted type of red diamond rings is the Red Garnet.