The following suggested standards are subject to the

• Grounding conductor (“ground”): wires must be bare, green, or green/yellow striped
• Grounded conductor (“neutral”): wires must be white or gray
• Orange, when used in a 3-phase 4 wire delta configuration supplying 120/240, shall designate the “wild” leg with 208v to neutral.
  • Orange is the only ungrounded conductor specified by the NEC. “Wild leg” (120/240 center-tapped neutral delta configuration), the two end phases on the center-tapped winding provide 120 volts to neutral, but on the wild leg you will find nearly 208 volts to the neutral. If you see an orange wire in a panel, alarm bells should go off: You don’t want to wire a 120 VAC circuit across the wild 208 volt phase.

• Grounding conductor (“ground”): wires must be bare, or green/yellow striped
• Grounded conductor (“neutral”): blue.
• PEN (Protective Earth/Neutral, combined) conductor, when insulated, shall be marked by one of the following methods:
  • Green-and-yellow throughout its length with, in addition, light blue markings at the terminations, or
  • Light blue throughout its length with, in addition, green-and-yellow markings at the terminations

• black, red and white

• black, red, blue and white

• black, orange, blue and white

• brown, violet, yellow and gray

• brown and white
• brown and blue¹⁾

• brown, purple, yellow, gray
• brown, purple, yellow, blue

• http://en.wikipedia.org/wiki/IEC_60446
• https://en.wikipedia.org/wiki/Electrical_wiring#Color_code
• http://www.allaboutcircuits.com/vol_5/chpt_2/2.html
• Comparison of NFPA/NEC & IEC Wiring Standards - Free (login)