Neither would having them all brown.I would have thought that one of the important reasons for having conductors 'identified' was to assist one in ensuring that they are connected to the correct terminal - and an 'identification' on/around the terminal would definitely not achieve that!
They only have to be, by regulation, identified as Line etc.; not which of several Lines.
You can do that with a pen.
I am only thinking of domestic; not complex boards.