I just did a home hair coloring from blonde to a dirty blonde, half way down my hair it tuned grayis

Get an appointment, go to the salon and fix it!

I just did a home hair coloring from blonde to a dirty blonde, half way down my hair it tuned grayish...help??

Discoloration like that is often due to uneven porosity in the hair...due to some kind of damage (chemical, heat related, sun, not getting trims, etc).

There isn't much to do really...except strip out the color with a color corrector, use a protein treatment to fill in the hair (ApHogee protein treatment and moisturizer are my suggestions), then try again...you may want to see a professional to fix your hair...if I could see or touch your hair, I'd be more helpful. Sorry.