The secondary means of identification is the color code of the marker. The exact colors are contained in the ANSI Z535.1 Safety Color Code.
Color is the secondary means to identification but many times the most important. The color of the marker should be used to identify the characteristic hazard of the contents of the pipe. The following chart list the classifications shown by ANSI / ASME A13.1 2015 as the suggested color combinations for the pipe markers.