In Colour Spaces, the hue, saturation, lightness colour space was introduced. In Lightness (Tone), lightness (also called tone) was discussed in detail. This page discuses the last two of the HSL triumvirate: hue and saturation. These together form the chromatic component of colour.

Saturation

In most paintings made before the modern era (which can be approximately defined as starting in the 1860s), the saturation values look very similar to those of the lightness. Shown in Figure 1 is a painting by the French artist Jean-François Millet (1814-1875) together with its lightness (below left) and saturation (below right) maps. Their similarity is clearly apparent.

Figure 1. 'Portrait of Louise-Antoinette Feuardent', 1841, Jean-François Millet (1814-1875)

In 1839, Michel-Eugène Chevreul (1786-1889) wrote ‘The Laws of Contrast of Colour’. Though it was intended for use by the design and printing industries, it had a significant impact upon the way that artists thought about colour. Taking the lead in this new thinking, Eugène Delacroix (1798-1863) was the first to knowingly and aggressively unlink saturation from lightness. Shown in Figure 2 is a painting by Delacroix together with its lightness (below left) and saturation (below right) maps. See how different the saturation and lightness maps are.

Figure 2. 'Still-Life with Lobster', 1826, Eugène Delacroix (17998-1863)

This effect is even more noticeable in the work of the impressionists, such as the example shown in Figure 3 by the French artist Claude Monet (1840-1926). See how in the lightness map (bottom left), the boat is the center of attention, whereas in the saturation map (bottom right) it is the sun.

Figure 3. 'Impression, Sunrise', 1872, Claude Monet (1840-1926)

Hue

Hue defines the angle of the color on the color wheel. It can also be understood as the 'name' of the colour (red green, blue etc). Colour name is also sometimes called the colour term.

This makes it very different to lightness and saturation, which are expressed as degrees of intensity. This can make thinking about hue in an exact manner rather difficult.

You will find that the most useful way to address colour is through its antagonism and variety, which are addressed in the following sections.

Hue antagonism

Two hues are understood as being very antagonistic to each another if they are very different. So... red and purple are quite similar, and therefore of low antagonism. Red and green are very different to each other and therefore of high antagonism. High antagonism is a property of complementary colours, which are colours that are located on opposite sides of the RYB hue wheel. Colour complementaries are introduced in Colour Spaces. Shown in Figure 4 is a simple profile expressed in three antagonistic pairs: red/green, blue/orange and yellow/purple.

Figure 4. Three sets of complementary pairs

Shown in Figure 5 is a painting by the French artist Jean-Francois Millet (1814-1875). See the strong red/green antagonism.

Figure 5. 'Classical Landscape', 1872, Jean-Francois Millet (1814-1875)

Even in un-colourfull paintings there is hue antagonism. Shown in Figure 6 is a predominantly brown painting sketch by the Dutch artist Rembrandt (1606-1669). In the bottom image, the colours have been treated in order to exaggerate the hue of the two browns that the painter used to show their strong red/green.

Figure 6. Top: 'John the Baptist Preaching ', 1635, Rembrandt (1606-1669). Bottom: a saturated version of the same image

Colour temperature

Colour is sometimes expressed in terms of temperature. This is a particular way of describing hue antagonism very commonly used by filmmakers and photographers. It assumes that colours on the purple/green side of the wheel are cool, and all others are warm (Figure 7).

Figure 7. The hue wheel separated on a warm/cool axis

Charmingly, colour temperature is also relative. Of any hue pair, one is likely to be warmer/cooler than another. For example, in Figure 8 is shown two yellows: the warm yellow of a sunflower compared to the cool yellow of a lemon.

Figure 8. Colour temperature expressed in relative form

Traditional Painters will often describe the difference between two versions of the same hue in terms of relative temperature. The warm/cool primary pairs many of them use are shown in Figure 9.

	Warm	Cool
Yellow	Lemon Yellow	Cadmium Yellow
Red	Alizarin Crimson	Cadmium Red
Blue	Prussian Blue	Cobalt Blue

Figure 9. The warm/cool primaries of a painter

Hue variety

Hue variety refers simply to the amount of perceptually different hues in an image and is easy to understand. In Figure 10 is shown a painting with low hue variety, next to a painting with high hue variety, both by the Spanish artist Pablo Picasso (1881-1973).

Figure 10. Two paintings by Pablo Picasso (1881-1973), showing high (left) and low (right) hue variety