Box dye over highlights?

[scaredfriend]

I unfortunately had to cancel my hair appointment last week due to poorly kids and can’t get another appointment before the next one I had booked in 5 weeks’ time. I have a full head of highlights - my natural colour is mid/light brown with quite a bit of grey coming through now. I have the highlights toned to a dark blonde / light brown.
Anyway, my roots are now very grey and my highlights are looking rather yellow/blond as the toner has faded over the summer. I don’t relish having to put up with this for another 4 weeks.
If I chuck a semi-permanent box dye over the lot - mainly to cover the roots and remove the yellow highlights - will it look awful? I figure that by the time I see my stylist at the end of September most of it will have faded / washed out so I’ll be good to go with my usual highlights. Or is this a terrible idea?

I do this on a regular basis between appointments. My stylist advised me it's fine and told me which colour to use. Basically a mid colour - so the over blonde / grey parts get toned down but the darker parts are unaffected. A semi permanent can't lighten darker hair but will darken lighter hair. Mine goes to a more honey colour when I put the semi on. And it lasts for quite a while.

I do this with no problems. It works well and my hairdresser says it’s fine to do if you do the roots and avoid the ends.

It’s fine I’ve done it for years just be careful of “hot roots” the hair nearest the scalp is new and dyes quicker .. so I put it on the rest of the hair and the top for the last 15/20 minutes otherwise the colour doesn’t come out the same - I also use a comb that is just for hair dyeing to comb it through so there’s no lines .. and use a a hair conditioner around the scalp and ears so it doesn’t dye them ! I’m a pro at this !

Thanks for the reassurance. This is exactly what I needed to hear!