I've never seen GM add an interior color mid-year. Exterior, sometimes, but only on special edition trucks like the Centennial Edition Silverado from 2018. GM always introduces regular production colors at the beginning of the model year.
High Country is getting an additional interior color for 2023 so if ZR2 were getting one, it would be in the order guide and would state late availability if it wasn't going to be available at 2023 launch.
