Scarlet or crimson (3)
I believe the answer is:
red
I believe this is a double definition.
'scarlet' is the first definition.
(I know that scarlet can be written as red)
'crimson' is the second definition.
(I know that crimson can be written as red)
(Other definitions for red that I've seen before include "Warning light colour" , "Type of wine" , "Primary colour" , "Colour of garnets" , "Merchant flag" .)