What color will indicate if a circuit breaker has popped?

The correct choice is indicated by a white ring around the circuit breaker when it has popped. This visual signal is specifically designed to show the status of the breaker, making it easy for ground crew or maintenance personnel to identify that the circuit breaker has tripped.

Other colors commonly found in circuit breaker indicators may denote different statuses or functions, but the white ring serves a unique purpose in indicating a tripped condition. Using distinct colors and markings for various functions is essential in aviation maintenance to prevent confusion and ensure safety protocols are followed correctly.