I love this build, but painting the bumper white I believe would take something away from what you are currently doing. The black offers a badass contrast and white would just be lost. That being said, I have been wrong before and I will again. But if it were me I would paint it white, then you would know for sure. But please make it easy on yourself and paint a base coat of silver first or you will be using a lot of white. All the best...