Sad to see there's not much feedback on these threads
Ok here goes.
First of all, avoid using the 'hue and saturation' tool with the whole image. It messes up color, not just on the car but everywhere.
You did quite good job on here, even if there's some quality issues at some places like overall lightning and when you changed the blue. Then there's the way you placed the car on the bg. The edges looks a bit rough. Try to avoid these
Keep it up!