A diamond with the highest colour grade is a diamond with the least amount of colour. The highest colour is D, which indicates that a diamond is colourless, and therefore extremely rare and valuable. An E grade indicates minute traces of colour that can only be detected by an expert. An F grade indicates slight traces of colour. A diamond in the G-H range is near colourless, with traces of yellow generally visible only when compared with whiter diamonds. I-J diamonds are also near colourless, with colour slightly detectable to the unaided eye. K-M diamonds begin to display noticeable colour.