U.K. REVISION
As from April 2006, British Standard 7671 (the "IEE Wiring Regulations") stipulates that fixed wiring should follow the new "harmonized" European color coding system (already nicknamed "The Killer Colors" in some quarters due to the conflicts with the old system).
Old British system for reference:
Phase A = red
Phase B = yellow
Phase C = blue
Neutral = black
New system, allowed permissively from April 2004 and mandatory
[*] from April 2006:
Phase A = brown
Phase B = black
Phase C = gray
Neutral = blue
Alternatively, all three phase conductors may be brown and identified by labels L1, L2, L3.
Single-phase circuits are to use brown for the phase conductor, no matter from which phase it is derived.
The new system specifies the following for d.c. installations.
3-wire grounded circuit:
Positive = brown
Neutral = blue
Negative = gray
For a 2-wire grounded d.c. circuit, the grounded side should be blue, no matter which polarity, with the positive or negative "hot" being brown or gray as appropriate, according to the above standard.
For a 2-wire ungrounded d.c. circuit:
Positive = brown
Negative = gray
Protective earth/ground conductors are to be green/yellow in all cases.
[*] Note that "mandatory" in this sense means mandatory according to the Wiring Regs./British Standard, which does not necessaily imply compulsion in the legal sense.
