The most common and most likely answer to this crossword clue is the 9 letter word DYESTUFFS
I've seen this crossword clue in The Daily Telegraph
D
Y
E
S
T
U
F
F
S
Buddy explains!
The straight part
We know that "colours" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case colours = dyestuffs.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 DYESTUFFS mean?
DYESTUFFS noun- Any soluble pigment used for dyeing the hair, fabric, etc.