That's what you get for putting it in a bun. Next time, go to a professional.

Black hair is the hardest to get rid of, it takes multiple times of bleaching to remove all the color, if it's still black you missed spots. I suggest a deep conditioning because if you do it more you'll fry your hair.

Before settling on black hair, I did this so many times and never managed to get it right. Bleach bleach bleach! I was stripping my hair then bleaching it, and for a long time it was orange. I've even been bright orange and loved it. But even if your hair is naturally dark - Bleach!

now you're a calico. congratulations on making the species shift

Your first mistake was buying box color. Second was not bleaching it before putting blonde on it. Third was putting it into a bun while letting it process. Just go to the salon next time.

Are you sure blonde is not your natural hair color?

actually, when bleaching your hair, put a plastic bag, like a Walmart bag, over your hair so that it traps the heat that the peroxide and bleach give off, because it sets off a chain reaction, speeding up the process from root to tip. My hair is naturally dark as well, and this works every time. Or, if not wanting to really really damage your hair, go to your local Sally's, or some other beauty supply store, and get the L'Oréal highlight color, red or magenta works best, get the #40 developing creme, a dyeing bottle, and gloves. it'll cost roughly $20-25. Mix about half of the bottle of the creme with all of the highlight color (or all of the creme depending on hair length), shake it up and apply. After that, leave a bag on your hair, and let it sit for 45 mins to an hour, then rinse until water is clear.

First, you put it on a bun. Second, naturally black here is almost impossible to dye completely blonde at home.