For one thing, a diamond that is set into a piece of yellow gold jewellery will appear to be of a higher (less color) grade than it actually is. This is because the stone is seen in stark comparison to the bright yellow of the metal next to it. Many people appreciate this when buying stones that range in the K,L and M colors.
Whiter stones like those that belong to the D,E, and F colors can also be set into yellow gold jewellery as well, although they might fare equally well when mounted against the cold whiteness of platinum metal. The other yellowish stones (K,L,M) may look even more yellow when set into platinum or white gold mounts, purely because of the nearby visual comparison between the stone's color and the metal's absence of it.
Diamond Color Can be Sometimes Seem Affected by Factors Outside of its Color-Causing Trace Elements. The Presence of Fluorescence and the Chosen Jewelry Metal Type Can Also Change How We Evaluate a Stone's Color, Especially at First Glance.
Metals aren't the only thing that can make a diamond seem to possess more color than it actually has. Another property called fluorescence can also affect how we evaluate diamond color with our eyes. The presence of fluorescence in a stone means that it will also emit some amount of visible light when exposed to a source of radiation (including daylight). Most diamonds that possess fluorescence showcase it in a bluish tinge, which can sometimes make yellowish stones look less yellow, but can also allow whiter stones to look as if they possess a greater amount of color.
While fluorescence can make some stones look less colored, and others more colored, the general majority seems to side more with the absence of fluorescence as a better trait in diamonds today. Dealers may sometimes give a percentage discount for stones that have very strong fluorescence, and likewise put pricing priorities on those with a total absence of it.
The percentage can vary, we've seen many that range from about 3 to 6% off of industry price sheets (without yet factoring in dealer discount), but it's different from a case to case basis.
Many people also prefer the colored glow that fluorescence provides. Some diamonds with a very strong bluish fluorescence can have a slight ethereal feel to their appeal.
