I had my hair bleached from Asian black to near white 3 or 4 times. You cannot do this at home. In order to remove the pigments in my hair. My colorlist had to use the strongest bleach possible for human hair 3 times! My scalp blistered one time. So you may want to bleach your hair just off the scalp.
Depends on what color you want to dye your hair to. You might now need to bring your base color to near white which is a step away from melting your hairs off your head (which happened to me once as well -just a little). Black hair will go to redish brown > orange > yellow > white if you keep applying bleach to it. Basically, you need to bleach your hair lighter than the color you want to dye your hair to. The lighter and brighter the color you want to dye your hair to. The whiter you will need to bleach your hair. If you want blue hair, you can’t start with yellow hair because you will get green as results.
You really need an experienced colorlist to do this because there are so many things can go wrong. Your hair might not be bleached evently. Or your hair doesn’t take the color as well as they should. They can fix things with other products…more colors or toners etc.
I hope I talk you out of if doing it youself. You really need to ask your colorlist if they have experiences on what you want done before you sit down. Good luck!