blue...

"The power of profound meaning is found in blue, and first in its physical movements (1) of retreat from the spectator, (2) of turning in upon its own centre. The inclination of blue to depth is so strong that its inner appeal is stronger when its shade is deeper. Blue is the typical heavenly colour.[...The halos are golden for emperors and prophets (i.e. for mortals), and sky-blue for symbolic figures (i.e. spiritual beings).] The ultimate feeling it creates is one of rest.[Supernatural rest, not the earthly contentment of green. The way to the supernatural lies through the natural. And we mortals passing from the earthly yellow to the heavenly blue must pass through green.] When it sinks almost to black, it echoes a grief that is hardly human.[As an echo of grief violet stand to blue as does green in its production of rest.] When it rises towards white, a movement little suited to it, its appeal to men grows weaker and more distant. In music a light blue is like a flute, a darker blue a cello; a still darker a thunderous double bass; and the darkest blue of all-an organ."
w. kandinsky, concerning the spiritual in art.