Colour refers to the degree to which a diamond is colourless. Diamonds can be found in many colours, however white-coloured or colourless diamonds remain the most popular. Diamonds are graded on a colour scale which ranges from D (colourless) to Z. Warmer coloured diamonds (K–Z) are particularly desirable when set in yellow gold. Icy winter white coloured diamonds (D–J) look stunning set in white gold or platinum. Nature has also created diamonds in shades of blue, green, yellow, orange, and pink. Red is the rarest of all. These diamonds are called ‘coloured fancies’ and are extremely rare and highly treasured.