Grey

Rich colours actually look more luminous on a grey day, because they are seen against a dark background, and seem to be burning with a lustre of their own. Against a dim sky all flowers look like fireworks. There is something strange about them at once vivid and secret, like flowers traced in fire in the grim garden of a witch. A bright blue sky is necessarily the high light in the picture, and its brightness kills all the bright blue flowers. But on a grey day the larkspur looks like fallen heaven; the red daisies are really the lost-red eyes of day, and the sun-flower is the vice-regent of the sun. Lastly, there is this value about the colour that men call colourless that it suggests in some way the mixed and troubled average of existence, especially in its quality of strife and expectation and promise. Grey is a colour that always seems on the eve of changing to some other colour; of brightening into blue, or blanching into white or breaking into green or gold. So we may be perpetually reminded of the indefinite hope that is in doubt itself; and when there is grey weather on our hills or grey hair on our heads perhaps they may still remind us of the morning.

-Daily News (quoted in Chesterton: Day by Day)