@heja,
Try one of the "Purple" Shampoos and Conditioners. There are several different brands on the market, I think they are useful to tone down the brassiness until you can get back to the salon. Sometimes the shampoo you use can strip some color out of highlighted hair.....for instance baby shampoo can take the toner out of the highlighted hair. The Purple Shampoos are a cheap way of correcting the color, don't use anything stronger until you consult with a licensed colorist.