Well then, there's clearly 3 paths to pursue here...
1. keep talking with him about it, while also consistently reassuring him that you love him and will never leave him, but that this is a sexual longing that you really need satisfied. hope that he comes around.
2. accept that this is never going to happen, and try to be happy with what you have
3. cheat
Some hubbys do come around after time with #1. I've seen it happen.
So far, I haven't met a woman who can stick with #2. But then, I do associate with a bunch of kinky, horny, girls, lol.
I'm not an advocate of cheating, but if you've tried #1 for a long time (years) and its going nowhere then it may be your only option. I believe we all deserve to life our fullest life. Hopefully, we find a partner who is willing and able to help us along that path. But if not, we may have to take responsibility for our own lives and our own satisfaction.
A 4th option is to leave the marriage and find someone who supports your interracial desires.