Color codes are used to identify conductors for point-to-point wiring and for circuit diagrams. The Insulated Cable Engineers Association outlines the color code in Standard S-73-532 in Annex E. The Standard breaks down the color code into methods of circuit identification. The most common methods used are Method 1, 3, and 4. After the Method is selected then the assembly of conductors must follow a color sequence from the tables with Table 1 and 2 being the most common.
National Electrical Code (NEC)
The NEC specifies that conductor colored white be used only as grounded conductors and that conductors colored green or green/yellow be used only as grounding conductors and that neither white nor green be used in any manner on ungrounded conductors. Tables 2 provide color sequences that do not include white or green conductors. If grounded or grounding conductors, or both, are used in the cable, they shall be colored white or green respectively, and inserted as the second or third, or both, designated conductor in the first sequence of circuit identification only. Where these conductors are required, they shall be specified.
Methods of Circuit Identification:
Method 1 - Colored Compounds
This method uses base color of insulation and uses tracers when needed, in accordance with Table 1 or 2. Base colors may be obtained by suitable color coatings applied to the insulation or jacket surface or by colored insulation or jacket compound. Tracers shall be colored stripes or bands marked on the surface of the insulation or jacket in such a manner as to afford distinctive circuit coding throughout the length of each wire. Tracers may be continuous or broken lines, such as a series of dots or dashes, and shall be applied longitudinally, annularly, spirally, or in other distinctive patterns.