I started coloring my hair when I was around 23 and have both done it myself and had it colored professionally. I found L'Oreal products to be the best, in the terms of the color longevity, color shade quality, ease of application, and impact on hair condition.
About two years ago (age 48), I decided to let it go natural. I was probably about 35% grey then. Not easy to do, since I don't have the face for short hair. Luckily, I have a superb stylist who figured out a way to do it so it looked decent.
I think it's a personal choice as to whether or not to color your hair as you get more grey. There definitely is a bias against older women, which is something to consider if you work at a place where that kind of thing is important. Do what makes you feel best. I am fortunate in that I got my parent's pure white, sparkly white and it looks fine w/my skin tone. In addition, my silver is in patches, so I look like I have white highlights. I've never been a girly girl---no make up, I wash/comb and go.