Have you ever had a really bad hair color experience? I have and I know they suck. I usually get it touched up every couple months but I try to make it last as long as possible. I've been using a purple shampoo for YEARS and still use it. If I think my hair is looking a little warm I leave the shampoo on like a mask in the shower for a few minutes then rinse and use conditioner. I can definitely tell after I use it because it takes out any brassiness and brightens the color. I've had to use this in the past to fix my hair when it didn't turn out right.
Since bleaching damages my hair so much I started using the Olaplex 3 at home treatment regularly. It's helped my hair sooo much especially with growing it out. The treatment isn't a conditioner or a mask so you still need to use a deep conditioner with it. I just put the Olaplex on an hour before I get in the shower and then shampoo and condition.