Warm vs. cool colors

"Warm" colors are often associated with daylight or sunset and the "cool" colors are often associated with a gray or overcast day.

Warm colors are often said to be hues from red through yellow, browns and tans included; cool colors are often said to be the hues from blue green through blue violet, most grays included.

Any color can be made to appear warm or cool by its context with other colors.

Color theory has ascribed perceptual and psychological effects to this contrast. Warm colors are said to advance or appear more active in a painting, while cool colors tend to recede; used in interior design or fashion, warm colors are said to arouse or stimulate the viewer, while cool colors calm and relax.

Most of these effects, to the extent they are real, can be attributed to the higher saturation and lighter value of warm pigments in contrast to cool pigments. Thus, brown is a dark, unsaturated warm color that few people think of as visually active or psychologically arousing.

Theory of Colours
Theory of Colors (original German title, Zur Farbenlehre) is a book by Johann Wolfgang von Goethe in 1810. It contains some of the earliest and most accurate descriptions of coloured shadows, refraction, dioptrical colours, and achromatism/hyperchromatism.

Goethe considered his own theory to be a more general explanation of colour, with Isaac Newton's observations being special cases. Goethe's work was not well accepted by the physics community of his day and is not typically discussed in modern accounts of the history of science. Physicists have come to understand, however, the distinction between the optical spectrum, as observed by Newton, and the phenomenon of human perception of colour. Developments in understanding how the brain interprets colours, for example colour constancy and Edwin Land's retinex theory, bear-striking similarities to Goethe's theory of colours—particularly his focus on brightness and contrast as the determining factors of colour perception.

When the eye sees a colour it is immediately excited, and it is its nature, spontaneously and of necessity, at once to produce another, which with the original colour comprehends the whole chromatic scale. A single colour excites, by a specific sensation, the tendency to universality. In this resides the fundamental law of all harmony of colours...

—Goethe, Theory of Colours, p. 317

Done in class:
The left row is the warmer colours while the right row is the cooler colours