Each wire shown in the diagrams contains a code which identifies the main circuit, a specific part of the main circuit, gage of wire, and color. An example would be A 2 18 LB/YL. This is a Battery Feed circuit, level two, eighteen gauge, light blue with a yellow tracer.COLOR CODECOLORBLBLUEBKBLACKBRBROWNDBDARK BLUEDGDARK GREENGYGRAYLBLIGHT BLUELGLIGHT GREENORORANGEPKPINKRDREDTNTANVTVIOLETWTWHITEYLYELLOW*WITH TRACER