Sun a strange blue? Such may be a puzzle! (7)
I believe the answer is:
soluble
'such may be a puzzle' is the definition.
(a puzzle is soluble or solvable)
'sun a strange blue?' is the wordplay.
'sun' becomes 'sol' (Latin for 'sun').
'a strange' indicates an anagram.
'blue' is an anagram of 'uble'.
'sol'+'uble'='SOLUBLE'
(Other definitions for soluble that I've seen before include "Can be converted to a liquid state" , "Lobules (anag)" , "Capable of being solved (in water?)" , "Dissolvable" , "Able to be dissolved" .)