Steps to reproduce:
1. Set a comp to Cinema 4D renderer
2. Add some text
3. Make it 3D, extrude the text and add some bevel
4. Add different colours to the front and bevels
5. See those lovely colours
6. Change the renderer to Mercury
Result:
The Bevel colour fills the text's front
Expected:
Bevel and front colours should remain as specified
System info
Application: After Effects (Beta) v23.1.0.71
OS: Windows v10.0.19044, RAM: 127.92 GB GB, CPUs (logical): 32