Why do we associate the colour blue with sadness and depression? You can feel blue, have or sing the blues. The third Monday of January is known as Blue Monday and is claimed to be statistically the saddest day of the year, though the study which first this has been debunked as pseudoscience. What can’t be argued, however, is that it’s also the name of a great New Order song:

Most people suggest we think of blue in this way because it’s calming, and that this effect is psychological, being derived from our association of the colour with the passivity of the sky or the hypnotic rhythms of the sea. And even though depression isn’t always passive or sad, it’s heavily associated with sadness, and we do imagine sadness as being a passive, stagnant state.

The science doesn’t quite back this up, but blue light does influence our minds. During the day, blue light increases attention and mood. Be warned though: blue light at night actually disrupts the production of melatonin, the hormone which controls our daily rhythms, and therefore disrupts our sleep. Counter-intuitively, if you need a night light, you’re best off with a faint red one, as it will have the least effect on your production of melatonin.

It’s counter-intuitive, of course, because red is the colour of danger and aggression in our minds. Which also seems quite logical: it’s the colour of blood and fire, we turn red when we get angry or get injured. I assume that most buttons that you MUST NOT TOUCH are red to deter us from them, but sadly the temptation of forbidden fruit is much stronger than that impulse. Though red has no effect on bulls, as they’re colour blind, so you could wave any colour flag in front of them. Or even better, just leave them alone.

One colour-based idiom I never understood is to be green with envy. What’s the association between green and envy? It occurred one day that maybe it’s because our envy is like a sickness (and I realised while on a ferry to the Aran Islands in very rough waters, that a person’s face really can turn green when they’re sick. I was quite pleased, after a little research,” that Shakespeare backed me up in that, referring to envy as “the green sickness in “Anthony and Cleopatra.” He and I are usually on the same wavelength.

Most of our colour-based idioms are based around blue or red, as they’re the colours with the strongest psychological associations (I’m not counting white and black as they’re so fundamental, and arguably, not strictly colours, though they may warrant their own post). One last curious colour-based idiom I want to look at is purple prose/purple patch. Though the latter is now more commonly used to refer to a period of good luck, both phrases originally had the same meaning: unnecessarily elaborate or flowery writing. It came about as a metaphor, referring to the practice of adding purple patches to clothes to make them look more luxurious, especially during Roman times when the colour was associated with the Emperor and other distinguished gentlemen.

Of course some colours, like pink and green, have connotations which have developed over time from social contexts, but it’s blue and red that have really gripped our imagination, as they’re the most fundamentally associated with nature. Though green has such as association too, so it’s no surprise that it’s become the colour of the environmental movement, and perhaps in the future that association will be so obvious that our descendants will assume the association was always obvious.