Hi, verynycegirl.  Is your color semi-permanent?  If it is it should fade down and wash out.
Highlights bleach the hair, it will be very damaging to the hair to rebleach it so soon.
Is this the first time coloring your hair?  If its not, and you've been going darker than your natural lighter color you can not go lighter again with out 1)bleaching your whole head or 2) grow out your natural color.  Another option that is super harsh is to have the color stripped from your hair.
It is extremely harsh and damaging and I don't recommend it.
If you really want to go to medium blond from where you are now, consult a professional colorist at a salon.  Everyone's hair responds differently to color, and red can be tricky!!
Good Luck, let us know how it turns out!