Alright mate, nice work. Here is a tip when changing a cars colour. Don't select anything, and go to Image-Adjustments-Hue/Saturation-Select blue from the dropdown menu in this case, remove saturation and then darken it.

This saves loads of time, and you don't have bits of blue here and there. Sometimes you'll get like another piece of blue, so just make a big square selection around the car.

Benni.