What is the meaning of the word "blue"?

Definitions:

any organization or party whose uniforms or badges are blue noun
- the Union army was a vast blue
blue clothing noun
- The police were dressed in blue.
causing dejection adjective
- a blue day
suggestive of sexual impropriety adjective
- a blue movie
the sky as viewed during daylight noun
- The archer shot an arrow into the blue.
to turn blue verb
- You are bluing.
used to signify the Union forces in the American Civil War (who wore blue uniforms) adjective
- a ragged blue line