I would feel weird wearing abelt from another style, unless it was VERY similar, at least in the kihon (katas can be learned quickkly if the Kihon is similar and sound). When I started back in Karate after a long break, I wore my white belt (under the same sensei) until my Son teste for his frist belt, then i went back to my old belt (6 months as a white), with my sensies approval of course.