Colour.
Colour is the element of art that is produced when light, striking an object, is reflected back to the eye. There are three properties to colour. The first is hue, which simply means the name we give to a colour (red, yellow, blue, green, etc). The second property is intensity, which refers to the vividness of the colour. We may describe a low-intensity blue colour as dull, subtle and greyed. A colour's intensity is sometimes referred to as its colourfulness, its saturation, its purity or its strength. The third and final property of colour is its value, meaning how light or dark it is.