This issue is new-to-Forza in Motorsport. The 2019 911 GT3 RS is missing two Paint Groups that were included in all previous titles with Advanced Painting. Currently it only has Paint Group 2 (all parts of the spokes l, excluding the Lizard Green outline), Inner Barrel and Outer Lip (barely visible).
In Forza Horizon 5, this car has separate Paint Groups for the outer part of the spokes, the inner part of the spokes, and the usually Lizard Green coloured outline
The 2019 911 GT3 RS is far from the only car in Forza Motorsport with missing Factory Wheel Paint Groups, but this should be fixed regardless.