Common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. The steering wheel features a removable brooch set with amethyst, topaz, and citrine stones. Other names for green quartz are vermarine, greened amethyst, or lime citrine. Sometimes amethyst and citrine are found growing in the same crystal. The citrine segments have oxidized iron while the amethyst segments are unoxidized. Although citrine occurs naturally, the majority is the result of heat-treating amethyst or smoky quartz. Other names for green quartz are vermarine or lime citrine. It is a diminutive of the Latin "citrinus" meaning citrine or light greenish-yellow. The original reference point for the citrine colour was the citron fruit. The term "citrine" refers to its yellowish colouration. Three improved versions of YFP are Citrine, Venus, and Ypet. The specific "citrea" is from Latin "citreus" meaning the colour "citrine". The first recorded use of "citrine" as a colour in English was in 1386. The system was successfully implemented by Fred Bramley and Walter Citrine. Citrine later moved to Brixham in Devon.