Best way to dye my childs hair?

My daughter is obsessed with black and purple and she’s on this kick for months for wanting her hair dyed those colors. Well I’m not ready for that just yet…but I may be willing to do strips of purple in her hair. What products would you reccommend that is not permanent, but will go away after washes? And if you’ve seen my post before, I’m trying to keep her self esteem going and at least trying to meet in the middle, I just don’t want to ruin her blonde hair.