Sounding appropriate, depressed tone (5-4)
I believe the answer is:
steel blue
'tone' is the definition.
(I have seen 'Metallic tone' mean 'steel blue' so perhaps 'tone' could also mean 'steel blue')
'sounding appropriate depressed' is the wordplay.
'sounding' indicates a 'sounds like' (homophone) clue.
'appropriate' becomes 'steal' (appropriate can mean to steal).
'depressed' becomes 'blue' (I've seen this in another clue).
'steal' is a homophone of 'steel'.
'steel'+'blue'='STEEL-BLUE'
(Other definitions for steel blue that I've seen before include "metallic colour" , "Metallic tone" .)