Go into photoshop and select all of the white areas on the car. You can use the Laso, or the Wand on a setting of ~22. then color the car red with an opacity of ~40% or whatever suits you best. Then keep the areas selected, and go into the Saturation area in the menus. now you can change the hue to any color you want on the fly and see it as you slide the hue bar. Hope this helps
