It depends on the color that you use and the products you use afterward. Use a good sulfate-free shampoo, color-protectant conditioner, things like that. And also, rinse with cooler water, rather than hot. That's what worked for me, personally. I have done reddish-brown, which faded rather quick. And blonde, after I bleached it. But my favorite was mixing aqua (one of the brights) and turquoise to make a mermaid look, which I did in October and it's now over 2 months since I did it and it's still the same color it was when I dyed it.