The colour of pearls often varies due to the type of mollusc. However, there are many other influences that can change the colour of the pearl including the temperature of the water, diet and pollutants. It is impossible to predict the colour of pearls whilst they are inside the mollusc as they vary widely even in the same hatchery. The most popular and idealistic pearl colours are pure white and pink but there are many other beautiful colours that can be naturally achieved.
Black pearls are hardly ever completely black and often are tinged with green, blue, grey, peacock, aubergine and many more. The most popular colour for black pearls to be tinged with is green. The pearl farms located in the French Polynesia, Indonesia and the Philippines produce naturally coloured black pearls. Pearls are often colour-treated and can be bleached or tinted to change the colour.
When pearls are graded for their colour, three characteristics are taken into account. The bodycolour which is the basic colour of the pearl, the overtone which decides if the pearls bodycolour is tinged with another colour and the orient which are the rainbow colours that appear as the pearl is rotated.