A curious state of affairs

Yesterday there was a full moon on the horizon, just as dawn broke, sitting on top of the long wall of the levees - not that we call them that here. Driving along, if I could have stopped, I could have placed any one of a dozen shapely bushes against its bright white face. Closer to work, stuck in traffic, the moon placed itself in perfect composition with a distant copse. By contrast, the previous morning, I had driven into the face of an angry sky. The clouds had been ripped into a crowd of small, black, ragged faces, all shouting down at the world. Behind the sky was changing from black to a strong but pale blue. Once, it occured to me, I would have described the colours in the sky in angry terms. Today I saw a grain of blues which reminded me of an old doorway, where layers of different blues had all worn away in runs and lines and blisters of paint. It called to mind, in the oddest way, a memory of a page in a school journal, with ink of one shade of blue fading, to be replaced suddenly by a richer, deeper, but different shade of blue, and a teachers words in blue biro against the margin. It called to mind the changing, rippling shades of blue on a boat in a remote fjiord as the sky faded, just as this one was coming to life.

Where did it come from, this shift in the source of words for colour.