a brunette to a blond wash out

Someone`s probably told you this already, but: You can`t lighten your hair temporarily. Hair can only be lightened with dyes that contain bleach, and bleach is never temporary. Some dyes say they are not permanent, and the dye in them is not, but the bleach is. There are some things you can do to lighen/highlight your hair temporarily in a very subtle way, but you can`t go brown to blond without it being permanent.