I started getting some greys when I was about 21, and now I have noticeable (to me) amount, but because my hair is blonde, other people don't notice. I've used a home hair dye a few times which covers it really well and is super easy to apply, so maybe that would be an option for you? It's well overdue another lot of dye, but the colour is pretty much the same as my hair so I've left it a while. It might be a good option for you though, as it is honestly very easy to do, and you can get decent dye for £10.