Orange (common color name / hue / variety / modifier): Abbreviated (O). A perceived colour hue resembling the average colour of the peel of the common or sweet orange (Citrus aurantium) . (See Fig. 9.97.) Orange is one of the spectrum colours, positioned between yellow and red , in the 590 nm to 630 nm wavelength region. Orange is also spoken of as being a warm colour. In the diamond trade, orange represents one of the basic twelve colour varieties. Orange diamonds can also contain secondary colour modifiers such as brownish orange (br-0), pinkish orange (pk-0), reddish orange (r-0), yellowish orange (y-0), and rarely greenish orange (g-0) . Orange can also occur as a secondary colour modifier in other colour varieties such as orangish yellow (o-Y), orange-brown (0-BR), etc. The range of colour tone for orange diamonds is quite variable in both lightness and saturation, resulting in pale (cantaloupe) orange, bright (flame) orange, dull (burnt) orange, and deep (marigold) orange colours. Since the majority of orange diamonds are somewhat dark, they tend to exhibit a tinge of brown such as brownish orange (br-0) or brown-orange (BR-0). Popular names for different mixtures of orange are amber, apricot, auburn, autumn, burnt, cantaloupe, carnelian, carrot , citrine, cognac, copper, flame (also known as “fire” coloured , see Streeter 1877), henna, hyacinth, mandarin, marigold , peach, poppy, pumpkin, salmon, sienna, and sunset