What is the right colour of a sapphire

The above picture shows a blue sapphire gemstone and its colour palette. The Colour palette is a list of main colours which occur in the picture.

The colour palette of the entire sapphire contains many diverse colour tones. Although many are blue they can be very different from each other.

However, if we consider parts of the sapphire and generate different colour pallets we can converge to a set of uniform colour tones.

A - The colour palette of the entire gemstone
B - The colour palette of an area with the desirable colour
C - The colour palette of an even smaller area with a more desirable colour tone
D - The colour palette of an area with a different colour tone

We may consider the colours on the palette 'C' as the colour of this sapphire. Why?

The colour you give to this sapphire is not just a property of this sapphire but partly how your brain interprets it. The brain picks the most desirable or the most attractive colour for you.

Not only the physical properties and your brain, but also the environment where you observe the gemstone also have a great impact on how you would see the colour of it.