In some languages, there are no separate words for blue and green; linguists call these colors simply, “grue.” Yet, in English, we have subcategories for every imaginable blue hue: sky-blue, azure, pale blue, navy, periwinkle, turquoise, baby blue, midnight blue, ultramarine, cobalt, grey-blue, true blue, and many more. Scientists tell us blue light will reset body rhythms for sounder sleep and higher alertness. Blue is sky and water; eyes and stones; slumber and spring — with summer right behind.

The color of the sky setting on the Charles River at twilight. 
Rose Lincoln/Harvard Staff Photographer
1The color of the sky setting on the Charles River at twilight. Rose Lincoln/Harvard Staff Photographer
The curve of the pillars and the curve of fallen snow are outlined against a Harvard Stadium walkway. Rose Lincoln/Harvard Staff Photographer
2The curve of the pillars and the curve of fallen snow are outlined against a Harvard Stadium walkway. Rose Lincoln/Harvard Staff Photographer
Look through a frosted window in subzero temperatures to see winter skies in Harvard Square and at Dudley House, beyond. Kris Snibbe/Harvard Staff Photographer
3Look through a frosted window in subzero temperatures to see winter skies in Harvard Square and at Dudley House, beyond. Kris Snibbe/Harvard Staff Photographer
The deep hues of a stained glass window at Harvard Divinity School frame a passerby. Rose Lincoln/Harvard Staff Photographer
4The deep hues of a stained glass window at Harvard Divinity School frame a passerby. Rose Lincoln/Harvard Staff Photographer
A magical pane of Divinity Hall stained glass.
Rose Lincoln/Harvard Staff Photographer
5A magical pane of Divinity Hall stained glass. Rose Lincoln/Harvard Staff Photographer
A horse and rider appear in color as they pass a barn window filled with work tools at Verrill Farm, where the Harvard Equestrian Club rides.
Rose Lincoln/Harvard Staff Photographer
6A horse and rider appear in color as they pass a barn window filled with work tools at Verrill Farm, where the Harvard Equestrian Club rides. Rose Lincoln/Harvard Staff Photographer
Blue light is better than white for resetting body rhythms scrambled by jetlag and shift work.
Kris Snibbe/Harvard Staff Photographer
7Blue light is better than white for resetting body rhythms scrambled by jetlag and shift work. Kris Snibbe/Harvard Staff Photographer
Zebrafish swirl in the Davidson Lab at Massachusetts General Hospital. 
Kris Snibbe/Harvard Staff Photographer
8Zebrafish swirl in the Davidson Lab at Massachusetts General Hospital. Kris Snibbe/Harvard Staff Photographer
A tinted pane of glass reflects an overcast day at Memorial Church.
Kris Snibbe/Harvard Staff Photographer
9A tinted pane of glass reflects an overcast day at Memorial Church. Kris Snibbe/Harvard Staff Photographer
Shades of indigo fill the sky at Peter’s Hill in the Arboretum, where the view of Boston is spectacular. Rose Lincoln/Harvard Staff Photographer
10Shades of indigo fill the sky at Peter’s Hill in the Arboretum, where the view of Boston is spectacular. Rose Lincoln/Harvard Staff Photographer
Science Center plants show steely optimism against a steely background.
Rose Lincoln/Harvard Staff Photographer
11Science Center plants show steely optimism against a steely background. Rose Lincoln/Harvard Staff Photographer
Australian butterflies preserved inside the Museum of Comparative Zoology.
Stephanie Mitchell/Harvard Staff Photographer
12Australian butterflies preserved inside the Museum of Comparative Zoology. Stephanie Mitchell/Harvard Staff Photographer
Samantha Faulkner was inspired by Picasso’s "Mother and Child" when she drew this picture and wrote, “A mother and son Sleeping together Maybe forever Gentle mother caring son Shades of blue Faces as pale as the moon …” Stephanie Mitchell/Harvard Staff Photographer
13Samantha Faulkner was inspired by Picasso’s “Mother and Child” when she drew this picture and wrote, “A mother and son Sleeping together Maybe forever Gentle mother caring son Shades of blue Faces as pale as the moon …” Stephanie Mitchell/Harvard Staff Photographer
Light beats down on Oakes Ames, who was a professor of botany and “dedicated his life to Harvard University.” The bust in his image wears a visitor's pin at the Harvard Museum of Natural History.  Rose Lincoln/Harvard Staff Photographer
14Light beats down on Oakes Ames, who was a professor of botany and “dedicated his life to Harvard University.” The bust in his image wears a visitor’s pin at the Harvard Museum of Natural History. Rose Lincoln/Harvard Staff Photographer
Under a clear sky, in a class titled “Winter Tree Observations,” Christina Curtis feels the soft bud of a pussy willow tree against her cheek.
Rose Lincoln/Harvard Staff Photographer
15Under a clear sky, in a class titled “Winter Tree Observations,” Christina Curtis feels the soft bud of a pussy willow tree against her cheek. Rose Lincoln/Harvard Staff Photographer
Harpist Erin Arai '08 calls her bagged harp “the giant blue mitten.” Rose Lincoln/Harvard Staff Photographer
16Harpist Erin Arai ’08 calls her bagged harp “the giant blue mitten.” Rose Lincoln/Harvard Staff Photographer
Blue velvet is worn by Sir Matthew Holworthy (c. 1608-1678), captured in oil on canvas.
Stephanie Mitchell/Harvard Staff Photographer
17Blue velvet is worn by Sir Matthew Holworthy (c. 1608-1678), captured in oil on canvas. Stephanie Mitchell/Harvard Staff Photographer
Green and yellow lily pads float in a blue pond at the Arboretum.
Justin Ide/Harvard Staff Photographer
18Green and yellow lily pads float in a blue pond at the Arboretum. Justin Ide/Harvard Staff Photographer
Sun speckles illuminate this rower under Weeks Bridge.
Rose Lincoln/Harvard Staff Photographer
19Sun speckles illuminate this rower under Weeks Bridge. Rose Lincoln/Harvard Staff Photographer
In the mostly green world of the Arnold Arboretum, Ian Brenner, age 2, and dad Jonathan add blue.
Rose Lincoln/Harvard Staff Photographer
20In the mostly green world of the Arnold Arboretum, Ian Brenner, age 2, and dad Jonathan add blue. Rose Lincoln/Harvard Staff Photographer