Understanding 120/240V Wiring Color Code | DoItYourself Understanding 120/240V Wiring Color Code Wiring Types. Depending on where you live, the branch circuit wiring in your home will be made.. Black and Red Wires. According to NEC, a black or red wire must be used as an ungrounded conductor,.. Blue, Yellow, and Other Colors. In systems where Wiring Color Codes | Color Codes | Electronics Textbook The colors adopted as local practice are shown in Table below. Black, red, and blue are used for 208 VAC three-phase; brown, orange and yellow are used for 480 VAC. Conductors larger than #6 AWG are only available in black and are color taped at the ends. US AC power circuit wiring color codes.