for me, personally, these were so awesome. i have had blue hair for about 6 years now, so upkeep has become a pretty routine part of my life. i would avoid washing my hair for as long as possible, because every shampoo would mean one step closer to recoloring. additionally, i stopped using a conditioner regularly because i would have to wash it again sooner. being able to replenish some of my color with conditioner has changed the game for me-- and it makes my hair feel so soft and healthy! i was amazed at how much color the in-shower dye actually deposited, both on hair that had been colored previously and on virgin roots.
i have not tried coloring over freshly bleached hair yet. if you are looking for vibrant color without having to lighten your hair, i might not suggest overtone as a starting point, but as far as maintaining my color goes, i think this is going to be my new go-to product. the ONLY negative thing i have to say about it is that it smells like a mild tea tree or mint, which i'm not a fan of, but it wasnt overpowering and it didnt stick to my hair for longer than a day.