I agree it's all really not about the hair. Glad to see so many deciding to let nature shine through on that.
Loved BlueHouse's insights and suggestions on this. Simple body language and use of voice is much of the game here. Another alternative to pounding a fist is to literally hold up your hand in the "stop" signal in the direction of the person interrupting you while you look at the others and talk (don't pause, obviously, and turn to them and switch to "I am still talking right now, listen to what I am saying." if necessary.) Not one to be used very often, but that gesture can be very effective. If someone is a frequent offender, so be shy about doing it more than once in a single meeting. The straighter your arm is, the more aggressive it will seem, so start with a bent arm if you want a more gentle "stop" signal. Not to be overused, of course, but sometimes necessary.
Gaining more professional presentation as a woman is a particular interest of mine, and something I've started researching extensively through reading and workshops. Here I am talking about a North American or Western European cultural context (other cultures have different subtle expectations). Some of the most common big issues I've seen when observing people introducing themselves "to the room" are:
Speaking too quickly, especially when saying their names. Slow down when you say your name. Make sure it is loud and clear. If your name is especially long or unusual, really practice this, because people in those situations tend to rush their names even more for some reason.
Not standing up straight enough. Head up, shoulders back.
Using qualifying language before most statements. For example, when asked to give one skill you bring to a new team, saying "I think I am good at . . . " or "other people would say I'm good at . . . " immediately makes you seem weak and unsure of yourself. Unfortunately these self-effacing speech patterns that many of us picked up as girls in an effort to fit in to classrooms. It would be better in that to say something very direct like "My expertise is in developing project strategies and statistical analyses."
Another one I've noticed is that women tend to say strengths like "I'm good at cooperating with lots of different people" or "I'm good at organizing the group." Pah, while I'm sure that's totally true, everyone already expects you are cooperative. Pick something they don't expect you to say, like, "I led the region in sales last year" or "I'm the fastest and most accurate CAD engineer in the west!"
Good luck!
PS I'm graying without dye.
