Hi! I get my hair dyed by professionals so that really really helps (considering I too am still learning the ropes) I used to have pastel pink hair so to get it white they first had to strip out the pink to reveal the bleached base underneath. As you probably know, bleached hair is usually a bit yellow so it isn’t exactly white like I wanted (also if you can I suggest getting your hair bleached by a professional). So my hair tech added some purple toner to my hair to balance out the yellow and make it white! I don’t know exactly what brand the toner was unfortunately :( but I maintain it with a silver (it really looks purple when it comes out) shampoo called Original Mineral Conquer Blonde Silver Shampoo so that my hair is still white a month after seeing my tech and it hasn’t turned yellowish. I hope this helps!