The natural pearl colour is a combination of the following factors:
• Body colour: the overall colour of the pearl
• Overtone: the one or more colours that overlie the body colour. On black pearls these colors are easiest seen on the lighter areas of the pearl, and in white pearls on the darker areas
• Orient: rainbow colours that are below or on the pearl's surface
• Hue: the tint and cast of the colour
• Tone: the lightness and darkness of the colour
• Saturation: the strength and intensity of the colour
The colour of a pearl will vary according to the type of host oyster, quality of nacre (if the nacre is too thin, the colour will look milky and lack overtone tints), environment they are grown in and trace-elements in those waters, and colour of the tissue that is inserted with the bead nucleus.
It is important to note that many pearls are artificially coloured. This is widely praticised with Freshwater pearls.
Apart from fancy colours such as dark gold, the rarest colours are the white, silver white and white rose. Every colour can have an overtone of pink or green. Ultimately, colour should be emphasized as a personal choice; no one colour is better than another if the quality and lustre are good. It is a matter of beauty and individual preference.