A person’s ability to distinguish different shades of colour is termed as colour vision. A person with normal colour vision can distinguish more than seven million different shades of colour.

There are three basic dimensions of colour-hue, saturation, and brightness. Hue is a property of chromatic colours. It refers to the name of the colour, e.g., red, blue, and green. Hue varies with wavelength, and each colour is identified with a specific wavelength. For example, blue has a wavelength of about 465 nm. and green of about 500 nm. Achromatic colours like black, white or grey are not characterised by hues.

Saturation is a psychological attribute that refers to the relative amount of hue of a surface or object. The light of single wavelength (monochromatic) appears to be highly saturated. As we mix different wavelengths, the saturation decreases. The colour grey is completely unsaturated.

Brightness is the perceived intensity of light. It varies across both chromatic and achromatic colours. White and black represent the top and bottom of the brightness dimension. White has the highest degree of brightness, whereas black has the lowest degree.