"should contain 4 items, not 3"

bpy.data.materials["chasis"].diffuse_color = (0, 0, 0, 1)

4th item would be Alpha in this case. Above line would be Black with opacity of 1.

"should contain 4 items, not 3"

bpy.data.materials["chasis"].diffuse_color = (0, 0, 0, 1)

4th item would be Alpha in this case. Above line would be Black with opacity of 1.

This, however, would be setting the Viewport Colour. To set the node base colour. Use this :

bpy.data.materials["chasis"].node_tree.nodes["Principled BSDF"].inputs[0].default_value = (0, 0, 0, 1)