I have tryed to lighten my dark brown hair with "Sun-in" and the part that I put it in shines orange (without a shine it looks slightly brown-orange). I would like to know how I can change the color of the "shine" to a bluish-purple color, or white (would white really look different as a "shine" or would it look natural?).

This might work for you: http://haircrazy.info/dyeingtechniques/refresh-your-permanent-hair-colour/