Mixture of red and blue (6)
I believe the answer is:
purple
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mixture of red and blue</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for purple that I've seen before include "Colour for aristocracy or emperors" , "Red and blue mix" , "Red and blue mixed" , "Colour associated with imperial authority" , "shade" .)