From my experience dont do both colours together - do your base colour one day and leave it a few days before doing the hi lights otherwise the two hair dyes will react with each and cause you hair to go like chewing gum. Or try the hair dyes you can get with the base colour an the hi lighter wand - think this is loreal (easy kit to use) Otherwise go to your hairdressers.
i used to have blonde hair with red highlights but they never stayed in very long, the hairdresser said its because red doesnt hold on to hair as easy as other colours and thats why it fades quickly