The most common and most likely answer to this crossword clue is the 4 letter word DYED
I've seen this crossword clue in The Guardian
D
Y
E
D
More clues leading to the result DYED
- Said to have gone out wearing fleece, unlikely to change?
- Said to have declined and changed colour
- Found out, Eddy coloured
- Dry head at intervals, having had shock treatment?
- Wheel tiny dodo out — it’s incurable
- Hardened criminal with old doyen swallows Ecstasy
- “It’s not natural” and once spoken, stopped working
- Hard-core, like an off-colour yarn?
- When found out, Eddy changed colour
- Coloured in untidy edges
Buddy explains!

The straight part
We know that "changed colour" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case changed colour = dyed.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does DYED mean?
DYED verb- To colour with dye, or as if with dye.
- Coloured or tinted with dye, or as though therewith.