Critical (Red): events that impair overlay network function

Major (Yellow): events that might impair performance of network

Medium (Blue): events that affect operation of network function

Minor (Green): events that might diminish performance of network

Critical (Red): These are the highest severity alarms indicating events that can cause significant impairment to the overlay network's functionality. Immediate attention is required to prevent major network issues.

Major (Yellow): These alarms indicate events that could potentially impair network performance. They are serious but not as critical as red alarms. They need prompt attention to prevent degradation in network performance.

Medium (Blue): These alarms are of medium severity and indicate events that affect the operation of the network function. They are important but do not require immediate action.

Minor (Green): These are the lowest severity alarms and indicate events that might diminish network performance. They are more informational and do not typically require urgent action.

Cisco SD-WAN Monitoring and Troubleshooting Guide

Cisco vManage Alarm Severity Levels Documentation