Which shampoo should i use to keep color in?

I like to dye my hair a dark Burgundy on top. for some reason my dark brown hair will only keep in color for 2-3 weeks max. I've used Ion color shampoos but those didn't work and then i switched to l'oreal everpure shampoo its ok.... My stylist says that no matter what i use my hair likes to spit the color out. any suggestions?