Under photo filters you can select a color. If you move pointer to an area over the car it will turn into a dropper tool so you can select the color from there. Then you can use the slider on the menu to adjust how light or dark you want to shade the area with the color. If you want to change the actual color uncheck the box that says preserve luminescence. That will make the bumpers the same color as the car.

I used the polygon lasso tool to circle all the bumpers and copy them to their own layer. I then desaturated them and adjustd the levels to make them look better. After that I did the filter to change the color.

Hope that helps. If I didn't have stuff to do I would take screen shots and show you.