A bargain in pink and blue (9)
I believe the answer is:
knockdown
'a bargain' is the definition.
(as in knockdown prices)
'pink and blue' is the wordplay.
'pink' becomes 'knock ' (both can mean to hit or strike).
'and' is a charade indicator (letters next to each other).
'blue' becomes 'down' (both can mean sad).
'knock'+'down'='KNOCKDOWN'
'in' acts as a link.
(Other definitions for knockdown that I've seen before include "Fell" , "Cheap - floor" , "very low" .)