Vivid shade of blue (5)
(Other definitions for azure that I've seen before include "Description of sky, perhaps" , "Shade of blue" , "Cerulean" , "Deep sky-blue colour" , "Sort of blue" .)
(Other definitions for ultramarine that I've seen before include "Deep blue pigment" , "Blue pigment originally made from lapis lazuli" , "Tone" , "one of the colours" , "See a colour" .)