My best wishes for your project.

Select all objects in question.
Object Manager> Tags> Render Tags> RS Object
Select all, and in the Object ID field, type num
Press Return and all objects will have an individual Object ID.
Now the ID can be used in the Material to specify any color via Ramp, while separately adjustable.

Since you wrote that you do it one by one currently, this would exclude AOV options to set colors.

https://help.maxon.net/r3d/cinema/en-us/Content/html/MeshObj_ObjectID_UserData.html

Is that what you are looking for? If not, please tell me more about your target.

Cheers