Color: fact, fiction and perception

John Singer Sargent painting using cooler light and warmer shadow.

Richard Schmid, in his book “Alla Prima”, described colors as “slippery devils with a logic all their own.”  He also warned us to be “wary of quaint beliefs, fears and expedient little rules.”
  
There is so much information and misinformation regarding color in painting, it’s difficult to decide what is important and what is not, but let’s give it a try.

First, to see color we need light. Light is a physical entity. Color is a perception. 

Seeing color is a response created by the brain interpreting light waves that hit our eyes. Our eyes have three types of cones, often referred to as red, green and blue. A more accurate description describes the cones’ responses to the wavelengths of light – short, medium and long wavelengths.

Here is an illustration of the wavelengths of visible light. Red has the longest wavelength and violet has the shortest wavelength. Note: This is NOT a scale of color temperature. Do not confuse wavelength with color temperature. We can, however, recognize how one color can turn into another by the change in wavelength. This is important.

The cones in our eyes are used to process color and luminosity during daylight conditions. Rods are used only in low light conditions. When it is dark we don’t actually see color since the cones are not active in low-light conditions. The exception is at the intersection of light and dark (e.g. dusk) when rods and cones can be active at the same time. At this brief time we see colors differently than during daylight. We do not see different colors but what we do see seems to be more saturated. This difference in color perception is probably because of a change in luminosity due to the activation of the rods.

Our inclination to associate some colors as warmer or cooler than other colors is not a scientific explanation of temperature. 

The distinction between warmer and cooler colors is based on a perceptual and psychological tendency to associate heat with warmth. We consider red, yellow and orange to be warmer than green, blue and violet. Color temperature is not an absolute value, as in warm or cool. It is a comparative value  of warmer or cooler (as compared to). So if you want to know if a red is warmer or cooler, to which red are you referring, and exactly what are you comparing it to? Alizarin is cooler than cadmium red, but it is warmer than ultramarine blue.

If you are looking for the science of color temperature, you will end up in a rabbit hole of contradictions. The Kelvin scale (used to measure the temperature of color based on black-body radiation) shows red to be the coolest color and blue to be the hottest color. Kelvins are, however, useful in astronomy, photography and studio lighting. This leads me to the next bit of interesting information . . .

The sun is not yellow. Actually our sun is white light, a mixture of all colors.

drawing from The Secret Language of Color

When the sun is low in the sky, it may appear yellow, orange, or red. But that is only because its short-wavelength colors (green, blue, violet) are scattered out by the Earth's atmosphere and only the reds, yellows, and oranges get to our eyes. The reason I mention this is the pervasive belief among some artists that yellow is the "warmest" color. The most obvious reason for this is our perception of the sun as yellow. Now, granted, this is a perception, and painting is all about perceptions, but the problem with this assumption leads to another rabbit hole of contradictions regarding the color temperatures of greens, blues and violets.

The pattern of color we see is red, orange, yellow, green, blue and violet. One color becomes another. We perceive color as a continuous spectrum, not as something with a beginning and an end (implying opposition), but as part of a whole. It is misleading to assign absolute values to these colors that exist in harmony with one another. When mixing color I consider red warmer than yellow and consequently, ultramarine blue as warmer than cerulean or thalo blue. In turn, green would be warmer than cerulean, but cooler than yellow. Following this pattern allows a pretty straight forward approach to mixing pigments - lighter, darker, warmer, cooler. One color will easily transition to another. It is not difficult to see the pattern of connection.   Ultimately, this is all about recognizing patterns and making comparisons. Color temperature is not an intrinsic property of pigment. It is the perception of one color as compared to another.

Color does not jump around randomly. Light determines our perception of color. Warmer light has cooler shadows. Cooler light has warmer shadows. The color we see changes as the light changes. Our perception of color can change according to what is next to or surrounding the color. Color can be elusive, ambiguous and sometimes bold. Find the pattern, design the connections, and pay attention to the subtlety of change.

Painting by Joaquin Sorolla - note the difference in color from one side of bench to other side.

for more information about our sun
The Yellow Sun Paradox by Stephen R. Wilk