I've used this bleach several times now, as I've been dying my naturally black hair red for years. I always reach for this to do the job, and it's always worked really well! I always leave it in for half an hour to an hour, and it turns most of my hair yellow/orange, and my roots ice blonde. It's really good if you want to strip your hair color; mind you, the bleach is really strong (every time I use it, it always mildly burns my nostrils), so do this in a very well ventilated area!
I recently decided to ombre my hair, and this worked perfectly for it as well. I did this in multiple processes. It lightened half of my hair medium brown in a mere few minutes, and I washed it out; I then applied it again to 2/3 of my ends for maybe 10-15 minutes and it turned light orange-ish brown; I washed it out again and applied it to the last third of my ends and it turned blonde. I did go back and add a bit more to the very end of my roots, and it turned a platinum blonde, which was nice.
Like I said though, the bleach is really strong and it did do a lot of damage to my hair, but the deep conditioner that came with it worked really well, just let it soak in your hair for a half hour or so and your hair will feel a lot better. Continue to use a hair mask or something a few times and your hair will be fine.
Of course, my hair is naturally black so there was a lot of brassiness, so a purple/silver/blue shampoo will be helpful! I'll continue to use this to lift my hair color, because it seems to be the only one that works this well!