Blush (6)
(Other definitions for colour that I've seen before include "Hue, tint" , "Blue or green, say" , "Hue, shade" , "black?" , "Quality that results from light reflection" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">blush</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that blush can be written as redden)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for redden that I've seen before include "Group of states under one head" , "Flush, become embarrassed" , "Evaluate the nature of (something)" , "Give visible sign of embarrassment" , "Reveal embarrassment in colourful way" .)