Blue seems to me the most mysterious and expressive of colors. Scientists have suggested that the human love of blue goes back to the days of caveman and some believe that the blueness of blue causes a physical alteration in the viewer. But because blue is a hard pigment to make-- Egyptian blue, ultramarine (the most expensive of pigments), lapis-- over centuries all were desired and expensive. In Medieval Europe blue was desirable because you needed it to paint things like the robes of the Virgin Mary.
It’s said that Michelangelo couldn’t finish his painting 'The Entoubment' because he ran out of money to buy the blue for the Virgin’s robes. And Vermeer squandered his entire family fortune on blue.
Of course numerous artists have devoted themselves to blue, perhaps most famously Picasso. Yves Klein wrotethat “blue has no dimensions. It is beyond dimensions.”