i'm looking for implementing Traffic light protocol for content visibility with Cerbos . what could be the best way to implement it? (TLP Visibility & Usage)

I am not familiar with TLP to give you a detailed answer. But, it looks to me like a matter of labelling the resources with their visibility level and checking whether the principal has the appropriate level as well. I think you may be able to define derived roles for each level with the conditions that principals need to satisfy and then write your resource policy rules referencing those derived roles.