yeah but the colour wouldnt come out right, the peroxide would over-rule the other shade
my hairdresser used toners to 'tone' down the peroxide a bit when i had highlights done and didnt like them, im quite dark and the peroxide stood out like a sore thumb, colour never lasted that long tho
I coloured over my highlights with a temporary dye and it came out fine. Now the colour is washing out and the hightlights are showing slightly and it looks perfectly ok.