The model has a composite map and multi-sub map. The eyes are composited over the diffuse color map, so changing the color will not disturb the eyes. The diffuse color map has a multi-sub map with 6 preset colors (white, blue, green, orange, pink, and turqoise). You can achieve your desired color out of these choices, simply by changing the object ID of the model.
The .Obj files are exported individually with the optimized setting for Maya, Mudbox, C4D, Blender, & Zbrush.