While talking about colour in diamonds, chemically pure perfect diamond has no hue. It means that such diamond has higher value. The colours are divided into: colourless (D,E,F), near colourless (G,H,I,J), faint (K,L,M), very light (N to R) and light (S to Z).
Also, the colour grade is a range of colour, where the gemologist or trained jewellery professional can compare such range with master stones.