Diamond: Not Necessarily Colourless

Fancy coloured Diamonds are not a mass-market product that are advertised everywhere and sold by the numbers. They have more personality than that. Fancy coloured diamonds are almost as much fun as coloured gemstones! Like coloured gemstones, each one is different. They come in spectacularly costly pale pinks and blues, pale to intense yellows, oranges, greens, and all those brown colours that are now being called names like cognac and champagne. So, buy a diamond instead of a coloured gemstone if you must, but at least contemplate a fancy coloured diamond which will give your jewellery more character, more individualism, more colour!
There are a many types of Diamond enhancements or treatments a Diamond can undergo that can considerably alter the price of the Diamond when compared to a natural Diamond.

Bleaching: The use of chemicals or other agents to lighten or remove a gemstone's colour to attain a brighter/whiter diamond.

Gamma/Electron Irradiation: The use of gamma and/or electron attack to change a gemstone's colour; may be followed by a heating process. Heating: The use of heat in a high temperature sintering furnace to effect desired alteration of colour, clarity, and/or phenomena.

Infilling/Fracture Filling: The deliberate filling of surface breaking cavities or fractures more often than not means with glass, plastic, opticon with hardeners and/or other hardened foreign substances to improve toughness, look and/or add weight. The foreign material will have a different index of refraction than diamond, and a trained gemmologist can see the light bending within the stone.

Lasering: A laser is used to go through a diamond and take away certain black inclusions. Chemicals are then used to further reach and alter inclusions in diamonds.

Oiling/Resin Infusion: The deliberate filling of surface cavities of a colourless oil, wax, natural resin, or unhardened man-made material into fissured transparent gemstones to improve appearance. (i.e., oil, man-made resin, paraffin, etc.)

Irradiation: The use of neutron attack, with the mixture of any other bombardment and/or heat treatment to change a gemstone's colour.

Diamond Fluorescence
Fluorescence as a term means that a diamond will glow (in blue) under a UV lamp when illuminated. It was used at first in diamond certifications as extra information for identification, but ultimately it began to affect the value of the diamonds.