don't do it, unless you are going to a pro, and even then...
Most women who color their hair in a way that you can't tell do a double process, a mix of base and highlights, that produces a more natural look (no one's hair is all one color all over). And most women wear their hair longer than men, so there's a growing out that also helps - the longer ends will change over time, and touch ups will focus on the roots vs. all over, lending again to that difference in each strand and getting closer to natural looking. Plus more women do it than men.
And...George Clooney. I mean if there was ever a case for embracing salt and pepper, imagine how stupid he'd look if he dyed it black ala ER.
It's unfortunately so easy to spot when a man has dyed his hair. If you are super tempted, get one of those washes out in a few shampoos types, and do it on a weekend, and ask the person you know won't mind telling you "nope, bad idea" to have a look. Then jump back in the shower and lather, rinse, repeat.