Open up your car image and select your desired cutting tool, i shall use the pen tool.

Select the whole back light.

Now with the light selected, and still with your desired cutting tool hold down the "ALT" key on your keyboard and cut around the lights in the middle. (may not be required to do this depending on type of lights).

Now goto "image > adjustments > channel mixer" and put a tick in the box at the bottom.

Thats it all done