wasn't this a song in late 90s

If you lack the skills to do a job call a friend for help. Or look it up online before you start.

Blue + yellow = green. To get truly blue hair you need to bleach it until white. Any yellow tones left will result in the dye turning turquoise or green.

even if you bleach first you still get blonde and the yellow will turn blue to green get a bleach kit with toner they sell one at Sally's but toner neutralizes the yellow in bleached hair allowing you to get the blue color you want (15 years of personal experience and a current cosmetology student)

Even though I hate spending money, I always go to a salon to get my hair done, to avoid this very scenario. Sorry OP, you'll get it next time!

Maybe if you quickly try and dye your hair firey orange-red you could pull off the Jennifer Lawrence look from X-Men

You were originally brunette, right? You bleached your hair, it turned yellow instead of blonde, you thought the blue would cover that up, so you applied the blue anyway? Nope. Blue + Yellow = Green hair. Your hair must be completely bleached with no yellow. Try waiting till the green fades, and then bleach it again (wait a few months or your hair will break off) and use a purple/blue toner for a few days to draw out the yellow from your hair. Or dye your hair back as close to its original color if it bothers you too much.

When anyone asks say its natural and wipe your hand from your nose to your hair. All 90's kids will remember that joke.

That's because you're an idiot and dyed blonde hair blue.. lol

im going to say you were a blond before you dyed your hair because that's what turns it green.