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What is the correct way to describe colour that we see?

Colour is described by three attributes. The following terms have been defined by the CIE and are given in Hunt's book "Measuring Colour":

• Brightness: the human sensation by which an area exhibits more or less light.
• Hue: the human sensation according to which an area appears to be similar to one, or to proportions of two, of the perceived colours red, yellow, green and blue.
• Colourfulness: the human sensation according to which an area appears to exhibit more or less of its hue.
• Lightness: the sensation of an area's brightness relative to a reference white in the scene.
• Chroma: the colourfulness of an area relative to the brightness of a reference white.
• Saturation: the colourfulness of an area relative to its brightness.

A 'colour' is a visual sensation produced by a specific SPD (spectral power distribution) incident on the retina. The eye senses colour using three classes of wavelength. This mechanism means that two different SPD's may produce the same visual sensation - an effect known as metamerism. A point to note, is that although the eye senses colour roughly according to red, green and blue light (trichromatic theory), higher visual processes in the brain code colour according to the opponent process theory using the opponent pairs roughly termed red - green, blue - yellow and black - white.