Quite sour nuts, greenish-blue (9)
I believe the answer is:
turquoise
'greenish-blue' is the definition.
(I've seen this before)
'quite sour nuts' is the wordplay.
'nuts' indicates anagramming the letters (nuts can mean crazy).
'quite'+'sour'='quitesour'
'quitesour' with letters rearranged gives 'TURQUOISE'.
(Other definitions for turquoise that I've seen before include "Bluey-green" , "Birthstone for December" , "Aquamarine colour" , "Greenish blue; gemstone" , "not quite green" .)