Colouring hair in certain areas?

[Helltotheno]

Just wondering if anyone has advice on colouring only parts of the head? I've managed to get away with no colour at all but now noticing whites at the front and sides and would like to colour those. Will this speed up the need for me to colour all of my hair? Will it make things worse?
Any advice welcome :)

I'd colour all over if you are wanting to hide grey hairs - you're very unlikely to get a colour that's such a perfect match to your natural hair colour that it won't be obvious if its not done all over.

Hair crayon?

www.amazon.co.uk/Roux-Tween-Time-Crayon-Dark-Brown/dp/B000TBY042

My grey bits come through quickest at the temples where they are most noticeable. I do colour just my temples if I don't want or need to do a full root colour. The only issue is it can be a bit of a waste of a whole packet of hair colour.