All objects are logically named and have own material of the same name.
There are 4 types of "body" and "tire" materials.Assign "body type 2" and "tires type 2"(or 3,4) materials to the body and tires to change the colors.

You can download high quality Renders : https://zaya.io/nt4n4 

9 objects.
The body textures are 4k pbr,The saddle textures are 3k pbr.
Reset Xform

Archive: Max 2015/obj+mtl/textures
System units: cm
polys: 180,358
verts: 180,865

Note : Who works with v-ray version lower than 3.1,pay attention to materials section BDRF(Microfaset GTR(GGX).

The wireframe render shows lowpoly topology.The Turbosmooth modifier is not collapsed.