Unless your family(or the family of the deceased person) are die-hard traditionalists, I wouldn't sweat it too much. Any color jacket, so long as it's respectful, should be fine. Even a dark sweater would probably work(make sure you have an idea of what the weather will be like. No sense in being physically miserable while you're also being sad.) Heck, before I transitioned, I wore a sun dress to a funeral. Not the most traditional of attire, but I don't think my mom minded.