Colin Rosenstiel wrote:
In article ,
newtonline{AT}gmail.com (Dave Newt) wrote:

Paris has colours, numbers or names (Yellow/1/Chateau de
Vincennes-Le Défense).

London has colours and names (Green, District).

So, from that point of view, Paris has three options to choose
whichever one you prefer; London has two.

The trouble is that Paris hasn't been consistent with colours. I
remember line 1 as red, 7 as purple, for example.

London hasn't been consistent either. Until 1934, the Bakerloo was red
and the Central was orange.

In both London and Paris, the colours are now consistent on all official
maps and on signage (well, on some signage anyway, and I don't think
either system has any signs with the wrong (old) colour). No doubt
someone will now prove me wrong!
--
Richard J.
(to e-mail me, swap uk and yon in address)