The only way to get your color to lighten is by using bleach. Using a lighter hair color does have some bleach in it to lighten, just a lower level of it. If you were to use a hair color (and you'd have to use either a medium or light blonde haircolor) you would probably only lighten to a dark strawberry blonde.
If you want actual blonde highlights you would definitely need to bleach it first. It may even need 2 bleach processes and you'd most likely need to leave it on for at least an hour
Also remember that any time you lighten or highlight, yyou will need to repeat this process once roots grow in.
I'm totally a DIY hair colorer, but even I would suggest going to a salon if you're going to do highlights.
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