I guess it's Light Purple.
Beginning January 1, 2019, the Department of Motor Vehicles (DMV) will begin issuing a single-color light purple Clean Air Vehicle (CAV) decal for qualifying vehicles pursuant to California Vehicle Code §5205.5. The new light purple CAV decal will be valid until January 1, 2023.
https://www.dmv.ca.gov/portal/wcm/connect/98b692f1-a43c-4d37-9fac-8e8cbe...
Beginning January 1, 2019, the Department of Motor Vehicles (DMV) will begin issuing a single-color light purple Clean Air Vehicle (CAV) decal for qualifying vehicles pursuant to California Vehicle Code §5205.5. The new light purple CAV decal will be valid until January 1, 2023.
https://www.dmv.ca.gov/portal/wcm/connect/98b692f1-a43c-4d37-9fac-8e8cbe...