You would want to make all the trim the same. But I'd use a wood trim and either stain it or paint it around a curved edge unless it was a very wide curve and the ceramic trim would make the bend within reason. Or you could cut up the trim into smaller pieces to make the turn but I think it would look worse than wood trim. Anyways I'd would think stain would be better than painting the trim.
Most wood trim comes sanded and ready to go.
And grout would look awfull and not hold.
Oh and one more thing. Companys like Schluuter make trim systems for tile. They may make something for this situation. I'd check with your local floor covering supply store. The place where the installers buy their stuff from, glue, tools, tackstrip, trim.....etc. A couple company names around here are Shoreline, Boone, and also some carpet retail stores can order stuff from their distributors.