Sapphire is one very versatile stone. People generally associate it with colour blue sometime not knowing that there is sapphire in almost any colour. Sapphires with colour different than blue are reffered to as fancy colour sapphires. Being corundum, a crystalline form of aluminium oxide, sapphire in its pure form is a colourless and transparent substance. Chemical impurities are the cause of the colour and depending of their presence when the stone was forming different colours came about. Very small quantity of the mined natural corundum is suitable for gemstone material. As general rule of thumb, transparent material, in bright saturated colour, free of grey or brown overtone are the major qualifying factors.
As this article is focused on fancy colour sapphires, the colour blue is not discussed. So is the colour red since the red corundum is well known under the name of ruby. Some colours of fancy colour sapphires are more popular than other but by my opinion lack of information plays big role here:
Pink sapphire is maybe second in popularity to blue. From very faint and delicate to opulent and rich hot pink bordering with ruby colour. The border where a pink sapphire qualifies for a ruby is very stretchy and personal. Of course is tempting for the gemstone dealer to present a hot pink sapphire for a pinkish ruby, since the name ruby is associated with much higher prices. It is however the same stone and one have to rather believe to one’s own eyes.
When more blue is present the pink turns to lavender purple going all the way down to deep purple hues. Many blue sapphires have either purple or greenish hue, but the ambiguity here is much less than with the ruby. There is something royal in a saturated purple sapphire.
Yellow sapphires are available in all hues and saturation. From pale greenish canary yellow to highly saturated golden yellow hue.
Deep orange is the variety associated with the Songea mines in Tanzania. Some stones can also be mistaken with rubies. When light and medium saturated the Orange sapphire turns peach or pinkish orange and it is then called Padparadsha. Padparadsha sapphire is quite rare and pricey if untreated but beryllium treated (pale material heated in the presence of beryllium) natural sapphires achieve stunning colours and are very affordable.
Green is not a sapphire colour. The green has usually brown overtone and although I have seen some nice stones, I am yet to see one that even remotely resemble emerald or tsavorite green. It is however alternative for people who prefer green stone which is tough enough to withstand every day, all condition wearing.
Last but not least in the family of fancy colour sapphires is the colour change sapphire, which in South Africa comes mainly from Madagascar. In natural daylight the stone has a complex greenish purple colour which changes to rubelite bluish red under incandescent light, a very interesting, and attention grabbing stone for engagement ring with a difference.