Cover that is inverted, turning red and blue (9)
I believe the answer is:
eiderdown
'cover' is the definition.
(I've seen this before)
'that is inverted turning red and blue' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'inverted' is a reversal indicator.
'turning' says the letters should be written in reverse.
'and' is a charade indicator (letters next to each other).
'blue' becomes 'down' (both can mean sad).
'ie' reversed gives 'ei'.
'red' in reverse letter order is 'der'.
'ei'+'der'+'down'='EIDERDOWN'
(Other definitions for eiderdown that I've seen before include "what may be on tonight" , "Warm bedcover" , "Find cover" , "thermal insulation" , "what keeps retired people warm" .)