When neither is religious, being of different religions isn't a big problem. I'm white, raised conservative Jewish. Hubby is Mexican, raised Catholic. Both pretty lapsed in faith, let alone specific religion.
I know of a couple, both white. She is devout Christian of some group. He was raised Catholic, even went to a seminary for a while. Is now not only atheist, but thinks religion is a crutch at best, and ridiculous. Yet, they have been very well together.