[HillBilly]

For people unfamiliar with industrial wiring I have included this image. This seems to be a standard used by most manufactures of control panels (I used a CNC for the example). The gray wires are usually black but this is a gray area. Shielded wires are omited in the drawing and could have any color jacket and conductor combination.

Darek

[Al_The_Man]

Darek, Also there is a provision in the 'Electrical Standards for Industrial Machinery' that allows for conductors that remain live when the main disconnect is off , this is usually circuits that originate from another panel etc, and in N.America the colour should be yellow (Orange in European standard).
For those involved in Machine building or retro-fit, the E.S.I.M ( see above) is a handy reference, it is an extension of the Electrical code as used by US & Canadian industry and is published by the NFPA http://catalog.nfpa.org .
Al