My natural hair color is dark blonde but I keep it very heavily highlighted. Last week I got my usual hilites and ask for a few lowlites. The lowlites turn out med brown instead of caramel and my all over hilites aren't light enough. I want to know if I put 20-30 volume developer in some shampoo apply then leave on for 10-15 minutes if it will lighten the lowlites and all over hilites? Also, does bleach need to be included in this mixture. Lastly, what are measurements for each ingredient? Thank you in advance for ant advice.

I don't advise you to use any form of bleach to lighten your high low lites, it would effect your over all hair colour as well. Sorry, we can't tell you the measurements, only a hair technician can do that.