Heraldic blue (5)
I believe the answer is:
azure
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">heraldic blue</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for azure that I've seen before include "Light blue" , "Description of sky, perhaps" , "Heraldic blue" , "Blue like the sky" , "Deep sky-blue colour" .)