Although I detest la grisaille, I love the word. La grisaille is a noun that means grayness; it can be applied to both the sky and to life. Parisiens use it a lot, because life in the city is often harsh, and also because in winter la grisaille hovers over the 20 arrondissements, making every street, building and lamp post look as though it were drawn by Edward Gorey.
The effect is gloom in the most stylish way, but after a while you forget about how cool everything looks and just sink into shallow depression.
In his book Paris to the Moon, Adam Gopnik describes this phenomenon perfectly:
"After a first winter in Paris, when the lure of the chimney and cigar smell holds you in thrall, you become accustomed to them, and then all you notice is the dark. From November to April, hardly a single day when you see the sun. The light itself is beautiful, violet and gray, but it always looks as if it were planning to snow, and then it never does."