Facilities must ensure that electrical receptacles or cover plates supplied from the life safety and critical branches of the essential electrical system are distinctively colored or marked, in accordance with NFPA 99 standards. This requirement helps staff quickly identify which outlets are on emergency power circuits during normal operations and emergencies.
View official sourceK917 Electrical Systems – Essential Electric System Receptacles Electrical receptacles or cover plates supplied from the life safety and critical branches have a distinctive color or marking. 6.4.2.2.6, 6.5.2.2.4.2, 6.6.2.2.3.2 (NFPA 99)