Paradoxically, [Blue] is the only one of all the colors which can be legitimately seen as a close neighbor to, as well as essentially symbolic of, dark and light both, oddly black in the night and almost white at the horizon by day. ('… deep blue air that shows,' observes Philip Larkin, 'Nothing, and nowhere, and is endless …') It can darken, it can obscure, it may float to and fro like a mist, evoking serenity and power. It might be said to be not so much a color as a state of the light. It is also the Void: primordial simplicity and infinite space which, being empty, can contain everything or nothing.
∆ Alexander Theroux, from “Blue”, The Primary Colours: Three Essays