Red Amber Green / Rot Gelb Grün

According to thrillist.com, stoplights are not only red due to its long cultural association with danger, but also as it has the longest wavelength of any colour on the visible spectrum, and can therefore be seen from the greatest distance.

Working on my schoolboy mnemonic ‘Richard Of York Gave Battle In Vain’, we start with red, then orange/yellow, then green - so traffic lights sensibly use the most visible colours, in that order.

But then why would our crucial ‘blue light’ vehicles be allocated a colour from the less visible end of the spectrum?