What are the most common colors for pilot lights?

The main purpose of pilot lights is to serve as indicators of the current status of some device or equipment or process. An alternate function, and not less important, of pilot lights is concerned with safety. According to the NFPA (National Fire Protection Association) a pilot light gives an indication to attract the operator's attention or to indicate that a certain should be performed. 

Color code for pilot lights

Most common types of pilot lights

The most common pilot light colors, as related to control panels, are:

• green pilot lights indicate that an equipment has been turned-on or started or that its operation is normal. The same applies for a control circuit. It would also indicate a safe status as related to the operator's safety. In this case green pilot lights are commonly used;
• red pilot lights indicate that an equipment has been turned-off or stopped due to a failure. About a control circuit it would indicate an emergency, due to a failure for example. In could also be used to indicate a situation of danger to the operator;
• yellow pilot lights indicate an abnormal operation of an equipment but not necessarily that it is turned-off. These color light may also be understood as visual an alarm for warning.

Pilot lights

Any question? Write in the comments and I shall try to help.

Other stuff of interest

• About PID controllers
• Ways to control a process
• Solving the Colebrook equation

==========

Ildebrando.