A primary colour in subtractive colour systems and a secondary colour made by combining red and green at equal intensity in the RGB colour model. Yellow is between orange and green on the spectrum of visible light. It is evoked by light with a dominant wavelength of roughly 570–590 nm.
Carotenoids give the characteristic yellow colour to autumn leaves, corn, canaries, daffodils and lemons, as well as egg yolks, buttercups and bananas. These absorb light energy and protect plants from photodamage in some cases. Sunlight has a slight yellowish hue when the sun is near the horizon, due to atmospheric scattering of shorter wavelengths (green, blue and violet).
Because it was widely available, yellow ochre pigment was one of the first colours used in art; the Lascaux cave in France features a painting of a yellow horse which is 17,000 years old. Ochre and orpiment pigments were used to represent gold and skin colour in Egyptian tombs, and in murals in Roman villas. In the early Christian church, yellow was the colour associated with the Pope and the golden keys of the Kingdom, but it was also associated with Judas Iscariot and used to mark heretics. In the 20th century, Jews in Nazi-occupied Europe were forced to wear a yellow star. In China, bright yellow was the colour of the Middle Kingdom and could be worn only by the emperor and his household; special guests were welcomed on a yellow carpet.
According to surveys in Europe, Canada and the United States, yellow is the colour people most often associate with amusement, gentleness, humour and spontaneity, but also with duplicity, envy, jealousy, avarice and, in the US, cowardice. In Iran, it has connotations of pallor/sickness, but also wisdom and connection. In China and many Asian countries, it is seen as the colour of happiness, glory, harmony and wisdom.