bluː/

adjective

1. of a colour intermediate between green and violet, as of the sky or sea on a sunny day.
"the clear blue sky"

synonyms: sky-blue, azure, cobalt (blue), sapphire, cerulean, navy (blue), saxe (blue), Oxford blue, Cambridge blue, ultramarine, lapis lazuli, indigo, aquamarine, turquoise, teal (blue), cyan, of the colour of the sky, of the colour of the sea"she had bright blue eyes"

2. informal

(of a person or mood) melancholy, sad, or depressed.
"he's feeling blue"

synonyms: depressed, down, sad, saddened, unhappy,
melancholy, miserable, sorrowful, gloomy, dejected,
downhearted, disheartened, despondent, dispirited,
low, in low spirits, low-spirited, heavy-hearted, glum,
morose, dismal, downcast, cast down, tearful;

noun

1. blue colour or pigment.
"she was dressed in blue"

2. a small butterfly, the male of which is predominantly blue while the female is typically brown.

verb

1. make or become blue.
"the light dims, bluing the retina"

2. historical

wash (white clothes) with bluing.
"they blued the shirts and starched the uniforms"