Reply To: black color not black?

I think that is because with the diffuse BSDF only, there is no glossy component. That is why before the Principled node ever existed, people used to mix diffuse with glossy always. But with the principled node you have lots of things integrated by default, that is glossiness and fresnel and all those kinds of good stuff. So probably the wheel on the right is not totally black because it is reflecting your environment.

Try mixing your diffuse and glossy and you’ll probably get a result similar to the principled.