Hair Dye Advice

Several months ago, I used a semi-permanent/temporary 24 shampoo hair dye on my hair. The color was blue black, which I have used before and which has previously always washed out of my naturally dark brown hair several months after application. However, after my last dyeing, which involved the very same color and type of a different brand, the color has yet to wash out of my hair. I have defined roots and want to know if my hair will ever release the color or if I am doomed to have wig-black hair until I cut it off. My interest is in permanently dyeing my hair my natural dark brown without keeping the unmaskable black.