vas glow'd, beyond e'en Nature warm is from a poem by Oliver Goldsmith dated 1764. Cold (the original contrast adjective for warm) appears earlier, in an English translation of Cours de peinture par principes (1708) by the French art historian Roger de Piles.
Warm and cold were, with dry and moist, terms used from the Middle Ages through the 18th century to describe a variety of animal and physical qualities. Warm described animation, exertion, ardent feeling or a complexion glowing with fever; cold described a lack of enthusiasm, sociability, life force or energy. There was a long tradition of metaphorical "warmth" from which the artistic usage grew.
Although the warm/cool contrast was familiar to artists since at least the early 18th century, it was to my knowledge first presented within a color wheel by the English artist Charles Hayter, in his Introduction to Perspective (1813). This shows that pairs of colors opposite each other on the hue circle are complementary colors, and that the warm/cool contrast is a "metacomplementary" relationship "the mother of all complementaries" between warm hues (from yellow to red violet) as a group and the cool hues (from yellow green to purple) as a group.
the first warm/cool color wheel diagram
from Hayter, 1813 (sky blue is placed at top, because in Hayter's time it was defined as the "purest" or most fundamental color; note the 19th century contrast with cold rather than cool)
Whenever you see a tidy geometrical icon in color theory writings, you can be sure that it represents something well cooked but only half baked! Despite the assurance and certainty expressed by Hayter's diagram, there are four questions that the traditional warm/cool usage has not clearly answered:
1. What are the warm (warmest) or cool (coolest) hues?
2. Is every hue in the color wheel either warm or cool, or are some hues excluded as neither warm nor cool?
3. What explains the visual or design effects created by warm or cool colors?
4. Why is the warm/cool contrast fundamental to our visual response to color and to the manipulation of colors in painting?
What Are the Warmest (Coolest) Hues? As Hayter's diagram indicates, the most common choice for the warmest hue is usually an orange or red orange with a CIELAB hue angle around 40 to 45. This includes red orange paints such as perinone orange (PO43) or pyrrole orange (PO73), or slightly darker orange red paints such as naphthol scarlet (PR188), pyrrole scarlet (PR255), cadmium scarlet (PR108). The principal criterion here is that these scarlets are among the most intense pigments available. However burnt sienna (PBr7) is the best choice for a dull red orange among earth orange paints.
Some artists prefer orange paints such as cadmium orange (PO20) or benzimida orange (PO62) with a CIELAB hue angle around 50 to 55. Orange hues are lighter valued, very intense and balanced between yellow and red.
The coolest color is whatever provides the complementary contrast to the warmest hue already selected colors opposite red orange or orange in a visual hue circle, as found in the Munsell Color System or in CIECAM. These indicate that the coolest hue is a blue or green blue with a CIELAB hue angle around 220 to 235. There are few pigments in this region of the color wheel, but they include manganese blue (PB33), phthalocyanine cyan (PB17) and cerulean blue (green shade, PB35). Pigments on the fringes include phthalocyanine blue (green shade, PB15) and cobalt teal blue (PG50).
But artistic practice has not been unanimous. An important and fairly common alternative is to choose yellow as the warmest hue. This usually means choosing an intense orange yellow paint, such as hansa yellow deep (PY65), nickel dioxine yellow (PY153) or nickel azomethine yellow (PY150), a dull earth yellow paint such as yellow ochre, gold ochre or raw sienna (PY43), or an intense yellow paint such as hansa yellow (PY97) or cadmium yellow (PY35) as the warmest pigment. Then a violet blue paint (ultramarine blue, PB29) or a blue paint (cobalt blue, PB28 or iron blue, PB27) are usually effectiv