 
		
		Definition of blue:
		
								
				"the phrase "feeling blue" was coined from a custom among old deepwater ships to fly blue flags or have a blue band painted along the hull if the vessel lost a captain or officers during a voyage."
			
			
	
		
		
		(n) :
		
		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; one of the 
colour balls used in 
snooker with a value of 5 points
		
 
			
	
		
		
		(v) :
		
		to make blue; to treat the surface of steel so that it is 
passivated chemically and becomes more resistant to 
rust