Melissa Beth
While my blue and green lasted for months (and we couldn't freaking get rid of it) my purple hasn't lasted as long, which I remember from having purple before. Like someone said, in between shampoos, just do a conditioner treatment without washing. Use dry shampoo. That's the best advice I have. Some colors are just divas 
Posts by Melissa Beth
Whatever you do, don't apply it twice in a row. That's what I did years ago and it fried my hair. I don't know how my hair dresser did it recently. She said she used some enzyme? It was to get it from dark auburn to blonde so we could dye it purple. Even then, it didn't come out even (the blonde).