Yellow-Green

Yellow-green, sometimes called chartreuse after the pale green liqueur made by Carthusian monks, is the hue between yellow and green, and it takes its symbolism from the meeting of the two. It is above all the colour of new growth, the acid-bright green of spring buds and fresh leaves before they darken, so it reads as youth, freshness, renewal and the very beginning of life. That same brightness gives it an unstable, sometimes uneasy quality: strongly yellowed greens are also the colours of sickness, of bile and of decay, so like green itself yellow-green carries an ambivalence between vitality and illness. It has no distinct liturgical tradition of its own, colour codes historically treating it under the broader categories of green or yellow. As a named category it belongs mostly to modern colour theory and to spectrum-based systems such as the aura literature, where it is placed between the solar plexus and the heart, blending the yellow of intellect and the green of growth into a sense of expansion and fresh vitality.

Yellow-green is unremarkable in the symbolic traditions and central to how vision actually works, which makes it a useful place to set the two kinds of account side by side.

Human daylight vision is most sensitive at a wavelength of roughly 555 nanometres, which is a yellow-green. Under bright conditions the eye extracts more brightness from this part of the spectrum than from any other, which is why high-visibility clothing and emergency equipment are made in that hue rather than in red: the choice is photometric and not symbolic. Under low light the peak shifts toward the blue-green, an effect named for Jan Purkinje, which is why colours change their relative brightness at dusk.

The colour name most used for the hue in English, chartreuse, follows the liqueur made by Carthusian monks, and the colour sense is a nineteenth century borrowing from it. That is a late and shallow etymology compared with most of the entries in this list, and it is a reminder of how many colour names are simply the name of a thing that had the colour.

Pigments in this range were made by mixing rather than mined, and the mixture of a yellow with a blue or a green was as far as most workshops needed to go. There is no long tradition of a distinct yellow-green pigment, no ritual use recorded under a name of its own, and no correspondence in the classical schemes. It is a colour the eye is exceptionally good at seeing and that the symbolic systems almost entirely ignored.