Navy blue

from WordNet (r) 3.0 (2006)

navy blue
    n 1: a dark shade of blue [syn: {dark blue}, {navy}, {navy
         blue}]

from The Collaborative International Dictionary of English v.0.48

Navy blue \Na"vy blue`\, n.
   1. A dark grayish blue. Also called {navy}.
      [PJC]

   2. Prussian blue. [archaic]
      [Webster 1913 Suppl. +PJC]