blue meaning
EN
[bluː] [-uː] 
US UK WBlue
- Blue is the colour between violet and green on the optical spectrum of visible light. Human eyes perceive blue when observing light with a wavelength between 450 and 495 nanometres.
- The modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao.
- Blue has been used for art, decoration and as a clothing dye since ancient times.
- Surveys in the US and Europe show that blue is the colour most commonly associated with harmony, faithfulness, confidence, distance, infinity, the imagination, cold, and sometimes with sadness.
EN Blue 
- NounPLblues
- The colour of the clear sky or the deep sea, between green and violet in the visible spectrum, and one of the primary additive colours for transmitted light; the colour obtained by subtracting red and green from white light using magenta and cyan filters; or any colour resembling this.
- blue colour:
- A blue dye or pigment.
- Any of several processes to protect metal against rust.
- Blue clothing.
- The boys in blue marched to the pipers.
- (in the plural) A blue uniform. See blues.
- (slang) A member of law enforcement.
- The sky, literally or figuratively.
- The ball came out of the blue and cracked his windshield.
- His request for leave came out of the blue.
- The ocean; deep waters.
- Anything blue, especially to distinguish it from similar objects differing only in color.
- (snooker) One of the colour balls used in snooker, with a value of 5 points.
- Any of the blue-winged butterflies of the subfamily Polyommatini in the family Lycaenidae.
- A bluefish.
- (Australia, colloquial) An argument.
- A liquid with an intense blue colour, added to a laundry wash to prevent yellowing of white clothes.
- (Britain) A type of firecracker.
- (archaic) A pedantic woman; a bluestocking.
- (particle physics) One of the three color charges for quarks.
- The colour of the clear sky or the deep sea, between green and violet in the visible spectrum, and one of the primary additive colours for transmitted light; the colour obtained by subtracting red and green from white light using magenta and cyan filters; or any colour resembling this.
- VerbSGbluesPRblueingPRbluingPT, PPblued
- (ergative) To make or become blue.
- (transitive, metallurgy) To treat the surface of steel so that it is passivated chemically and becomes more resistant to rust.
- (transitive, laundry) To brighten by treating with blue (laundry aid).
- (transitive, slang) To spend (money) extravagantly; to blow.
- (ergative) To make or become blue.
- AdjectiveCOMbluerSUPbluest
- Of the colour blue.
- the deep blue sea
- (informal) Depressed, melancholic, sad.
- Pale, without redness or glare; said of a flame.
- The candle burns blue.
- (entertainment, informal) Pornographic or profane.
- The air was blue with oaths. a blue movie
- (politics) Supportive of, run by (a member of), pertaining to, or dominated by a political party represented by the colour blue.
- I live in a blue constituency. Congress turned blue in the mid-term elections.
- Illawarra turns blue in Liberal washout
- (astronomy) Of the higher-frequency region of the part of the electromagnetic spectrum which is relevant in the specific observation.
- (of steak) Extra rare; left very raw and cold.
- (of a dog or cat) Possessing a coat of fur that is a shade of gray.
- (archaic) Severe or overly strict in morals; gloomy.
- blue and sour religionists; blue laws
- (archaic, of women) literary; bluestockinged.
- (particle physics) Having a color charge of blue.
- Of the colour blue.
- More Examples
- Used in the Middle of Sentence
- Methylene blue (MB, methylthioninium chloride) is a phenothiazine that crosses the blood brain barrier and acts as a redox cycler.
- The dork holding the torch — usually an eager first-time safari-goer - is soon sitting with eyes and lips clenched tight, turning blue from the effort of not inhaling bugs through his nose.
- The Blue Jays lead the game going into the ninth inning.
- Used in the Beginning of Sentence
- Blue arrows: RCA concatemerized product with higher molecular weight.
- Used in the Ending of Sentence
- I was thinking that you could use the same engine to put Atogs and big artifact creatures in, similar to the mono-brown deck with a splash of blue.
- Smaller flowers such as chionodoxa are better under shrubs where they can create great pools of blue.
- Fairhanded Spring unbosoms every grace, Throws out the snowdrop and the crocus first, The daisy, primrose, violet darkly blue.
- Used in the Middle of Sentence
Definition of blue in English Dictionary
- Part-of-Speech Hierarchy
- Adjectives
- Nouns
- Countable nouns
- Countable nouns
- Verbs
- Ergative verbs
- Transitive verbs
- Ergative verbs
- Adjectives
- en blues
- fr blues
- en blue-black
- en bluebird
- en blueberry
Source: Wiktionary
Grammatically, this word "blue" is an adjective. It's also a noun, more specifically, a countable noun. It's also a verb, more specifically, an ergative verb and a transitive verb.