I have customized quite a few sports cars, mechanically and exterior. I use a photo of the stock car and color . Load it in Adobe photoshop and add colors, grill components, etc.
You can download a free trial version of Photoshop. Try it out. It's like looking at a photo of your new paint theme completed. No guess work.Take a look at a 63 Austin Healey. The silver and white side version. Food for thought. Good Luck.