Colourful, sad music (5)
I believe the answer is:
blues
'colourful sad music' is the definition.
'blues' can be an answer for 'music' (blues is a kind of music). I'm not sure about the 'colourful sad' bit.
'sad music' is the wordplay.
'sad' becomes 'blue' (similar in meaning).
'music' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'blue'+'s'='BLUES'
Can you help me to learn more?
(Other definitions for blues that I've seen before include "colours" , "Australian redheads" , "Melancholic music of black American folk origin" , "Depression - music" , "Conservatives" .)