Can I assign a different material on the windshield in the body. The main body has red colour assigned Or only one base material is supported for now?
Yes. You have to create a submesh but first you must select the correct rendering mode. In the top right hand corner you currently have the left one selected. Pick the third one. Select the face you want to have a different color and on the right hand side select submesh, hover over to find. Once created select the icon in the bottom right hand corner and you will see all of you submeshes. You can change the color and a bunch of other settings for each submesh you create. You can have more that one face use the same submesh colors as well.
Interesting approach. Need to read up what a submesh is.