"blue" as noun
1 - 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.
2 - A blue dye or pigment.
3 - Any of several processes to protect metal against rust.
"blue" as verb
1 - To make or become blue.
2 - To treat the surface of steel so that it is passivated chemically and becomes more resistant to rust.
3 - (laundry) To brighten by treating with blue (laundry aid)
"blue" as adjective
1 - Of the colour blue.
2 - Depressed, melancholic, sad.
3 - Pale, without redness or glare; said of a flame.
