Warm and Cool Colors in Painting: Light, Shadow and Distance

Warm colors lean toward orange: the reds, oranges and yellows. Cool colors lean toward blue: the blue-greens, blues and violets. In a painting the useful question is which of two neighboring colors is warmer, because a blue can be the warm one next to another blue.

Temperature is a comparison

Winsor & Newton publish no chart of warm and cool paints, because a color's bias depends on the color next to it. Their example: the green shade of Ultramarine Blue is the cooler of their two ultramarines, yet next to Cerulean Blue it looks much redder, so it becomes the warm blue.

That's why painters talk about a warm and a cool version of each primary: cadmium red against alizarin crimson, a deep cadmium yellow against a lemon yellow. Each is only warm or cool compared with the other.

The effect works on grays too. The painter George Clausen told Royal Academy students in 1904 that as long as the sunlight in a painting is warm, a shadow mixed from umber and white, or a plain gray, can be made to look blue or nearly so.

Light and shadow

Light has a color of its own. Photographers measure it in kelvins, and the numbers run the opposite way to a painter's words: the lower the number, the redder the light. Nikon's camera settings put an incandescent bulb at about 3000 K, direct sunlight at about 5200 K and shade at about 8000 K.

A shadow takes its color from whatever light still reaches it. Outdoors on a clear day, the sun is blocked but the blue sky still lights the shadow, so the shadow leans blue. The lit side gets the sun as well, which is far brighter and warmer. Hence the old rule: warm light, cool shadows. Clausen gave it both ways round. Outdoors in warm sunshine, the lights are warm and the shadows cool; indoors in ordinary daylight from a window, the lights are cool and the shadows warm.

It's a tendency that depends on the light sources, not a law. The painter and illustrator James Gurney is skeptical of fixed rules about warm and cool: when warm light is reflected into a shadow, or a second warm light reaches it, the shadow can be warmer than the lit side. Outdoors he notes that within a shadow, planes facing up toward the open sky tend to be cool, while planes facing down pick up warm light reflected from sunlit ground below. Before you mix a shadow, look at what is lighting it.

Temperature and distance

Air adds its own blue to anything far away. Leonardo told painters to make distant buildings "less defined and bluer", and the farther away, the bluer. Winsor & Newton put the same idea in terms of temperature: warm colors appear nearer, and cool colors recede. In a landscape, keep the warmest colors in the foreground and let the distance cool and soften.

Using it in a painting

• Decide the light first. Is it warm or cool, and what lights the shadows? Set the shadow temperature by comparison with the light, then check it against the reference.
• Mix value first, then temperature. Cooling a color with blue usually darkens it as well. Match the value, then shift warmer or cooler at that value. See value and color.
• Vary temperature inside a shape. A shadow painted at one temperature looks flat. Make the planes that face the sky a little cooler and the planes that face warm ground a little warmer, without changing their value much.
• Compare in pairs. Put two swatches side by side and ask which is warmer. A color's name on the tube won't tell you how it reads next to its neighbor.

Warm and cool in a reference photo

A camera adjusts for the color of the light. White balance is meant to make colors look natural whatever the light source, and some cameras have a setting just to remove the warm cast of incandescent bulbs. So a photo can be cooler, or more neutral, than the light you remember. See how to choose colors from a photo.

The palette from a photo tool labels each of a photo's main colors Warm, Cool or Neutral. It measures color in CIE Lab, where hue is an angle: 0° points to red and 90° to yellow. A color with a chroma of 8 or less, a gray or near-gray, is Neutral. Otherwise a hue under 130° or over 330° is Warm, which covers the reds, oranges, yellows and yellow-greens, and everything else is Cool. The line falls in the greens and at magenta, so an olive green reads warm and a forest green cool.

Those labels compare each color with gray, not with its neighbors. The warm and cool map does the comparison across the whole picture: it tints each part orange or blue by how far its color leans toward orange or toward blue. Set to compare with the photo itself, it measures against the photo's own average color, so even a photo with an orange cast shows which parts are warmer and which cooler than the rest.

Sources

• Winsor & Newton, "Is there a list of warm and cool colours for each of the Winsor & Newton colour ranges?": no fixed warm and cool chart, the ultramarine and cerulean example, and warm colors appearing nearer while cool ones recede.
• George Clausen, Six Lectures on Painting, Methuen, 1904, lecture III, "On Colour". Project Gutenberg. Warm lights and cool shadows outdoors in sunshine, cool lights and warm shadows in daylight indoors, and a gray shadow made to look blue against warm light.
• Nikon, "White Balance", Nikon Z f Reference Guide: what white balance is for, the kelvin values for incandescent light, direct sunlight and shade, lower color temperature being redder, and the setting that removes the warm cast of incandescent light.
• Christopher S. Baird, West Texas A&M University, "Why doesn't the outside world appear blue even though so much light comes from the blue sky?", 2014: shadows on a clear day are lit by blue skylight, and direct sunlight is much brighter.
• James Gurney, "Relative color temperature on skin tones", Gurney Journey, July 28, 2017: no fixed rules about warm and cool, and shadows warmer than the light under warm reflected or secondary light.
• James Gurney, "Downfacing planes", Gurney Journey, February 1, 2008: in shadow, upward-facing planes are cool and downward-facing planes warm.
• Leonardo da Vinci, The Notebooks of Leonardo da Vinci, translated by Jean Paul Richter, 1888, section 295, "Of aerial perspective". Project Gutenberg.
• Konica Minolta, "Let's look at some color spaces", Precise Color Communication: the L*C*h color space, chroma and hue angle in CIE Lab.