Conveniently sets the diffuse and ambient color of this at the same time.
See set_ambient and set_diffuse.
The default ambient color is (0.2, 0.2, 0.2, 1.0)
The default diffuse color is (0.8, 0.8, 0.8, 1.0)
| this | A Pipeline object | 
| color | The components of the desired ambient and diffuse colors |