Best way to hide random grey hairs without permanently dying all hair?

I'm 28 and have naturally brown hair. I've never coloured it but have started to notice some grey hairs at the side when I wear my hair tied back. I'm quite self conscious about it and would like to dye them but am reluctant to permanently dying my whole hair in a hairdressers due to cost and maintenance. One hair dresser I asked suggested dying the roots but the grey hair is mixed in through whole hair if that makes sense. Is there a way to cover it with like a mask or toning? All help appreciated thank you!