Just a little word of advice if you're specifically trying to dye your hair blonde don't do it out of a box, you'll never get the results you want. It's worth it to pay for a professional. Because by the time you get the results from box dye that you want then you might have paid the same amount as a professional.
Now, not all box dye is bad. If you have someone who won't botch it then sometimes you get good results depending on the color. Typically going darker than your natural color produces the best result. My friends and I have a happy habit of turning our dorm rooms into a ratchet hair salon. We go out and buy box dye from CVS or Walgreens then we come back, set one of the heart attack chairs in front of our small vanity/mirror and we dye hair. Not only have we gotten dye on ourselves but the floors too.
Our method of washing it out is to lean over the shower's edge, because we don't have a tub, and attempt to get all the color out. This plan worked for my friend who wanted to go from her brownish hair with blonde highlights to a deep red. We successfully didn't botch her hair color and she rocks it. It also worked for the spooky season when we dyed my hair dusty mauve, which is a purplish brown color. But it certainly doesn't work if you want to go lighter than you are.
Sad Story Time:
I realize I'm stupid for thinking that I could dye my hair lighter blonde out of a box dye. But here we are. I must have thought my hair was lighter than it really was too. But anyways, I bought a lighter shade of blonde from Walgreens and my friend Hannah dyed my hair. We let it process for the 25 minutes then I washed it out.
Double bad idea because my hair has ginger ish roots so the blonde dye only made it a really light orange. Here I am freaking out because I have a sorority photoshoot the next day and it's already 12 at night. So the next day I haul my ass to Walmart, hoping to find toner. I bought Oops color away and two different purple shampoo type deals.
Both of these proceeded to not work, they lessened the brassiness only slightly. In the light of my panic attack, my suitemates walked to CVS with me to see if I could buy hair dye that was slightly darker. Within like an hour or so of me having to meet my driver for the event, we re-dyed my hair. It still doesn't look good, despite my suitemates and roommates telling me it does.
So here I am waiting till Wednesday at 12 o'clock for a real professional to fix my hair. Slightly freaking out because I have a semi-formal on Friday and I don't want to look stupid. But it is what it is
Moral of the story: if your thinking about dying your hair.... just go to a hair salon and save yourself the trouble.