I agree with BlueHouse that it really isn't about the hair.
And, Heather, interrupting dudes is super fun! Especially when you notice how much they interrupt women. Like ALL THE TIME. I consider it my daily contribution toward dismantling the patriarchy.
Forgive me for a minute while I put on my ranting dress -- I feel like women are socialized to want to be well-liked more than basically anything else, and this works to our detriment in many ways but especially in the workplace. The thing that is worthwhile is not being well-liked, it's being well-respected.
My boss is the one who clued me into this. I was on a call with some of our (older, less flexible) team members (dudes) and they were giving me guff about a decision I made, and I basically smacked them down like "No, you are doing it the way I said, unless you can convince me otherwise and so far your arguments have not convinced me." After the call I said to my boss, "Man, I guess I was a kind of a dick." And he replied, "Yeah, you were, but who cares?"
Immediately I got the point that powerful dudes at work don't give a shit about everyone liking them all the time. They interrupt, they argue, they get their point across at any cost, and precious little of it is taken personally. And honesty? I think it's healthy ... because it's not personal, it's work, and the best idea should win. If I think I have the best idea, or if I see something terribly wrong with the idea on the table, I need to advocate for my point of view and not worry if others think I'm too aggressive.
Not to say that I'm a big old meanie all the time -- I try to make lots of jokes and I'm as helpful as I can be and in general I have good relationships with co-workers -- but I also have no qualms about taking up space and making sure my POV is well represented. If the decision goes the other way, I will work with it, but up into that point, I am straight-up arguing my POV, even if it gets heated.
I have no idea how you act at work so I'm just throwing this out there in case it might apply.
I should also say that I am fat, I am a weirdo, I wear strange clothes and make stupid jokes and I am not what anyone would picture in their mind when they imagine "a powerful woman at work." And yet, everyone listens when I speak. I think it's because I am firmly seated in the power of my own convictions, and I have a lot of confidence in my ability to think things through clearly, and I don't give a shit if the other people at the table don't like me in that moment.
All that being said, I fully intend to let my hair go gray whenever it wants to. I may overdye it hot pink or teal when I get enough gray for it to matter. At 42 I've got maybe 2-3% so we'll see how it goes ...
ETA: I think a lot of this is down to the industry, too. I'm in tech (albeit an old and moldy corner of tech) which I'm sure is different from finance, law, etc. Also I'm a physically large person -- 5'10" -- so that doesn't hurt either (though I am often seen as / treated like I'm much younger than my colleagues).
Basically, I don't mean to say "be like me and things will be great!" More that niceness is way over-emphasized as a life goal for women. I see it all the time at work -- the woman has a great idea but doesn't want to be seen as rude or aggressive so she backs down and we end up making a worse decision than we may have if she had spoken up. This leads to her feeling less valued and even less interested in / invested in work, and it becomes a vicious circle of disengagement and disempowerment.