Odd behavior with changing renderer.material.color

I want to change the color of one texture on runtime, so i went in with blender and separated the mesh by material. It worked for everything but the piece I want to change... But I realised that the other material was just a border around the material im trying to change so I went with it. When I call renderer.material.color = Color.black; it flips the material order in the inspector and only changes the color of the border? What on Earth is going on?