color (diamond colour)

Also colour is an extremely important factor in determining the diamond’s value.
Let us remind you that diamonds are the product of carbon crystallization: the purer the stone is, the more colourless and valuable it is. On the other hand, if it contains “intruded” molecules, it takes up different shadings and colours.
The shading of most diamonds offered on the market ranges between colourless and a very light yellow colour: their value decreases as their colour becomes more apparent.

The GIA classifies these stones according to a worldwide recognised colour scale which goes from the letter "D" (colourless) to the letter "Z" (bright yellow).

When the colour becomes more intense diamonds are called "Fancy". These are very rare stones whose value increases as the colour becomes intense. They are not classified according to official price lists, as each one is valued on the basis of its properties and inner rarity features.
They may have different colour shadings, ranging from the most “common” yellow (which results from its nitrogen content) up to the extremely rare red colour.