That’s not accurate. It varies within product family if it is cerakote or dyed polymer. There are some families with colored frames that are exclusively cerakote (e.g., Security-9).
It depends on the SKU.
https://ruger.com/products/ec9s/specSheets/3285.html
Grip Frame: Turquoise Cerakote®, High Performance, Glass-Filled Nylon
https://ruger.com/products/ec9s/specSheets/13200.html
Grip Frame: Turquoise, High Performance, Glass-Filled Nylon