Purple (hue / variety / modifier): Abbreviated (PP). A perceived colour hue resembling the gemstone amethyst, the lilac flower, or the robes formerly worn by sovereigns (i.e. , Royal Purple). The colour Tyrian purple, recorded as early as 975 6.C., was a purple dye prepared by the ancient Greeks and Romans from the glands of a particular sea snail (Murex purpura). Purple is a nonspectral colour, denoting a range of colours between red and violet on a colour wheel. Purple with tints of brown, pink, or red are spoken of as being warm colours; whereas, purple with tints of gray, black, and blue are spoken of as being cold colours. In the diamond trade, purple represents one of the basic twelve colour varieties. Purple diamonds can also contain secondary colour modifiers such as pinkish purple (pk-PP), brownish purple (br-PP), grayish purple (gy-PP), reddish purple (r-PP), and blackish purple (bk-PP). Purple can also occur as a secondary colour modifier in other colour varieties such as purplish red (pp-R), purple-pink (PP-PK), etc. The range of colour tone for purple diamonds is variable (mostly in lightness), resulting in pale (periwinkle) purple, bright (orchid) purple, dull (eggplant) purple, and deep (amethyst) purple colours. Popular names for different mixtures are amethyst, clover, desert glass, eggplant, grape, heliotrope, lavender, lilac, mauve, mulberry, orchid, periwinkle, plum, royal, and thistle