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NEC 1959
210-5. Color Code Where installed in raceways, as open work, or as concealed knob and tube work, the conductors of multi-wire branch circuits and two-wire branch circuits connected to the same system shall conform to the following color code. Three-wire circuits—one black, one white, one red; four wire circuits—one black, one white, one red, one blue; five-wire circuits—one black, one white, one red, one blue, one yellow. When more than one multi-wire branch circuit is carried through a single raceway the ungrounded conductors of the additional circuit may be of colors other those specified. All circuit conductors of the same color shall be connected to the same ungrounded feeder conductor throughout the installation.