Conductors connected to shunt trip breakers are marked with blue tape in this photo.
In addition to operating as a conventional breaker, a shunt trip breaker is designed to also be tripped by an electrical signal delivered by an additional conductor connected to the breaker. For example, if a fire suppression system were to activate, spraying water, a signal sent to trip breakers protecting electrical circuits in the affected rooms could help prevent electrocution.
You should see label markings indicating that the breaker is designed for this purpose.