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' (abbreviation for id est, 'that is' in Latin).
'inverted' shows that the letters should be reversed in order.
'turning' says the letters should be written backwards.
'and' means one lot of letters go next to another.
'blue' becomes 'down' (both can mean sad).
'ie' in reverse letter order is 'ei'.
'red' written backwards gives '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" .)