Once upon a time long ago, I dyed my pubes. I didn't bleach them or anything, but I added a blue dye to the hair, let it sit, then washed it off. It didn't take very well, but I thought it was amusing anyway, lol.
Oh... Goodness. Yes. I used henna. I'm dark blonde there as it is. Those close to me in sophomore year dubbed me "Fire Crotch." It doesn't wash out. It also stained the skin beneath my landing strip. Fun!