Architect Jones includes a bit of dark colour (6)
I believe the answer is:
indigo
'colour' is the definition.
(I know that indigo is a dye)
'architect jones includes a bit of dark' is the wordplay.
'architect jones' becomes 'inigo' (I've seen this in another clue).
'includes' is an insertion indicator.
'a bit of' says to take the initial letters.
The initial letter of 'dark' is 'd'.
'inigo' placed around 'd' is 'INDIGO'.
(Other definitions for indigo that I've seen before include "type of dye" , "A deep blue dye or colour" , "Violet dye" , "Natural blue dye" , "Settlement; New Mexico native" .)