What are the two types of flashing mode operations in traffic signals?

The identification of yellow-red as the two types of flashing mode operations in traffic signals is accurate because these colors typically serve distinct purposes in traffic management.

In flashing mode operations, yellow flashing lights are often used to caution drivers of a potential hazard, such as a pedestrian crossing or a school zone. This alerts drivers to slow down and be prepared to stop. The red flashing light indicates that the driver must stop completely at the intersection or the location where the traffic signal is installed. Thus, the combination of yellow and red in traffic signals effectively manages traffic flow and enhances safety by conveying critical information to drivers.

The other options do not represent established or recognized combinations of flashing operations in traffic signals. Green signifies go and is not used in a flashing capacity for signaling to stop. Blue is not typically used in standard traffic signals. Red-red does not correspond to a normal operational mode in the context of signaling. Thus, the selection of yellow-red encapsulates the two primary indications used during flashing operations in traffic signals.