Color mapping (sometimes also called tone mapping) dictates which color operations are performed between the user interface inputs and the values rendered and the way the rendered pixels are displayed through the VFB on the user monitor.
V-Ray default Color Mapping settings ensure a 1:1 mapping of all the user operations and the final result. For example, doubling a light's intensity exactly doubles its contribution to the final pixel, and cutting a shader's light reflectance in half cuts its contribution to the final pixel in half. This approach corresponds to Linear Workflow.
Changing the Color Mapping settings might be desirable for artistic purposes, but doing so will deviate from the linear correspondence between user actions and the rendered result, and will also veer away from physical accuracy in the scene.
To ensure the most accurate results, it's best to leave the Color Mapping settings at their default values and perform artistic color transformations during post-production. This will also ensure repeatability, consistency, and a very accurate rendered solution.
