Mesh has turned different colour after smoothing?

So I "Mesh > Smooth"'d my model to add more polys to it, which caused the mesh to turn black, I tried inverting the faces but it did nothing. I did try to apply a new shader to it, but then it turned all green, and the problem still persists. I've looked online but there doesn't seem to be a straightforward answer to this. I'm wondering if anyone here knows what could be causing the mesh to act this way?

Thanks