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