Ruby and scarlet (4)
I believe the answer is:
reds
'ruby and scarlet' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for reds that I've seen before include "These are not right" , "Colours for communists" , "First snooker balls to be potted" , "Scarlet and crimson, say" , "Left-wingers" .)