True Blue

“If a little kid ever asks you just why the sky is blue, you look him or her right in the eye and say, 'It's because of quantum effects involving Rayleigh scattering combined with a lack of violet photon receptors in our retinae.'”
~Philip Plait

Mystic Stones, São Vicente, Madeira Island.
photo by Eric Wüstenhagen

Blue
photo by Carl Jones

The Turquoise Room
photo by Megan Allen

Turquoise Skull
photo by Teofilo

Blue Skies, Blue Ocean: fishing boats, Provincetown
photo by Liz Kelleher

Study in Blue
by Jennie

Well Covered
photo by Emmanuel Huybrechts

Blue Angels, Idaho Falls
photo by Charles Knowles

Starry night over the Rhône
by Vincent van Gogh (1853–1890)

Another quote about the blue sky:

I thank you God for this most amazing day, for the leaping greenly spirits of trees, and for the blue dream of sky and for everything which is natural, which is infinite, which is yes.
~e. e. cummings