Lad never changes colour (8)
I believe the answer is:
lavender
'colour' is the definition.
(I know that lavender is a type of violet)
'lad never changes' is the wordplay.
'changes' indicates anagramming the letters.
'lad'+'never'='ladnever'
'ladnever' is an anagram of 'LAVENDER'.
(Other definitions for lavender that I've seen before include "Mauve flower, cultivated for its fragrant oil" , "Mauvish blue; shrub" , "Plant used in perfumery" , "Light bluish-purple" , "Plant with aromatic purple flowers" .)