Dark blue dye (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">dark blue dye</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for indigo that I've seen before include "type of dye" , "Blue-violet colour" , "Colour - I'd go in (anag)" , "Sixth rainbow colour" , "Deep-blue dye or colour" .)
(Other definitions for anil that I've seen before include "Dye for nail" , "Indigo (plant or dye)" , "name of man" , "Species of blue" , "Source of dye" .)