I took a red 2016 model Audi R8, and turned it orange with tools found in Photoshop. I took the pen tool and basically selected the entire vehicle. I then pressed a few simple buttons and was finally able to play around with the color of the vehicle. Thankfully, it doesn't do anything to white or black. Otherwise, those wheels might be pink.
Ever seen the British television series Sherlock? No? You uncultured swine. Surely you know Benedict Cumberbatch. Anyways, I added another layer then took the brush tool and just fooled around. Any stray green was taken away using the eraser. It's pretty simple.
Now this change isn't as noticeable. Mainly because it's a larger picture and isn't focused on the eyes. I changed the eye color the exact same way I changed the color of the Audi. I simply used the pen tool, cropped around the eyes to select them, and fooled around with colors. The change is more noticeable in the right eye. It was altered from blue, to a purple with some slight green.