One cuts copies up in colour (5)
I believe the answer is:
sepia
'colour' is the definition.
(sepia is a kind of colour)
'one cuts copies up' is the wordplay.
'one' becomes 'i' (Roman numeral).
'cuts' means one lot of letters goes inside another (some letters cut their way into other letters).
'copies' becomes 'apes' ('ape' can be a synonym of 'copy').
'up' says the letters should be written backwards (in down clue: letters go upwards).
'i' put within 'apes' is 'aipes'.
'aipes' back-to-front is 'SEPIA'.
'in' is the link.
(Other definitions for sepia that I've seen before include "Shade of brown, as in old photographs" , "Brown tint" , "Brown tone associated with old photographs" , "Sort of ink" , "Pigment got from cuttlefish ink" .)