It's the colour of the sky, the colour of the sea. Distant mountains. A hot flame. Forget-me-nots. A jackdaw's eye.
No other colour has that ability to swallow you whole, to wrap you up— you can't get lost in yellow or red, orange or green. Pablo and Yves knew it.
I once heard that the Ancient Greeks did not have a word for blue. Cerulean, cobalt, indigo, and oh ultramarine— beyond the sea— what beautiful words! Lapis lazuli, like some incantation, the stone that drove Titian wild.
It's the ultramarine that my palettes run out of first.