I'm 37 years old man and I have a lot of gray hair. I have been ignoring my hair for the past five years, but I'm now starting to get comments in regards to my age because of my hair.
I don't know a single thing about hair color. Especially for men. I've been researching online and I also spent time at the local pharmacy starring at the vast array of choices.
I just want my black hair to be black. Any men of Era color their hair? If yes, what products do you use? And how often?
If you are going down this path, and I don't think there is anything inherently wrong with dying your hair, it is probably best to start by having a professional do it, at least the first time. A hair stylist will be well placed to cut and colour you hair in a way that matches your natural colour in a good way. While they are doing it, you can ask questions about what colour they think it is, how often they think it will have to be redone, how to care for coloured hair etc.
You can do it yourself at home with equally good results, but if you use a home kit you should start by choosing a colour/shade that you would think is actually a little lighter than what you think your hair is. The fastest way to make dyed hair look unnatural is by going too dark, especially when talking about "black". If you think your "black" hair is actually black, choose "Dark Brown" to start. If you think your hair is actually "Dark Brown", choose "Medium Brown". A standard brand like Just for Men should do just fine, but make sure to read and follow the instructions very carefully (read all the way through before starting), and try to apply with care to avoid staining skin around the hairline or getting dye on your earlobes etc.
Either way, you'll need to repeat getting your hair dyed every 4-8 weeks if you want to keep the grey disguised. Exactly how often will come down to how you hair is styled (shorter, neater styles will show grey regrowth quicker), how thick you hair is (bushy or thick hair covers regrowth for longer), and how fast your hair grows (faster growing hair will obviously show regrowth faster).
Given your hair has already been greying for years and people around you are commenting on it, people will notice that you have dyed it and certainly some of them will comment on the fact you have dyed it. Be prepared for a range of comments, some positive, some negative on how it looks, some saying you should have left it grey and just "be yourself". If you stick with it, it will become normalized, and over time the comments will subside as people forget about it (and perhaps your preferred outcome is getting back to a pre-grey time where nobody bothered to comment on your hair at all). The thing to remember during the initial period is it is what you think of the results that matters, and you should stick with it or not based on how you feel about it, not others.