“Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm and on the frequency ~680–610 THz. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal mixture of red and green light. On a colour wheel based on traditional colour theory (RYB) where blue was considered a primary colour, its complementary colour is considered to be orange (based on the Munsell colour wheel).The English language commonly uses “blue” to refer to any colour from navy blue to cyan. The word itself is derived from the Old French word bleu.
In English, blue often represents the human emotion of sadness, for example, “He was feeling blue”. In German, on the other hand, to be “blue” (blau sein) is to be drunk. This derives from the ancient use of urine (which is produced copiously by the human body after drinking alcohol) in dyeing cloth blue with woad or indigo. It may also be in relation to rain, which is usually regarded as a trigger of depressive emotions. Read more Give me the Blue(s)