Doing this yourself can be very difficult and needs a professional. Try visiting your local salons for advice and ask them if they could provide a colour service for you on some of their training sessions. This way you would have a professional salon looking after you at a far lower cost. ...More >
The only think I would recommend to do at home (and it is totally dependant on what colour your highlights are?) is a colour that is totally temporary that washes out.
My advice would be visit your salon and ask what the options are.