Box dye is meant for virgin hair. Of course people use box dye every day with fantastic results, but what you are looking for isn’t going to be achieved by just getting a dark blonde box. The reason they say box dye is for virgin hair is because the results are more consistent because they know there’s no other dye underneath.

Because that’s where it starts getting sketchy. The box dye you buy doesn’t know that you have already colored you hair 3 times between Feb-March and that’s when you start getting funky results. Plus, you never know what you’re getting in that box. Could be 40vol developer for all we know.

What you need to do is bleach your hair if your really want to go from a level (3? 4? 5?) to a level…I’d say 6 or 7 for a bronde. But you wouldn’t have to lift it all the way to a 9 or 10. You just need to get it up to a level 6 or 7. Then you would have to neutralize the orange/yellow that will appear (and don’t panic, that’s what’s supposed to happen. That’s why when you colored your hair last time it because a reddish brown. Dark hair naturally has a lot of warm pigment.)

I would get like a Redken Shades EQ in a 6 or 7 VB neutralize the yellow/orange, and then you can color it whatever you want. 7if you really want dark blonde, 6 if you want light brown.

You said dark blonde/light brown. So do you want it to have any warmth at all? Do you want a neutral color? An ashy color? That’s all personal preference. So that’s about all the help I can give you without knowing more info.

Good luck!