Have you tried henna instead of the commercial dyes? It's available in many different shades, and my sister was able to keep a beautiful blood-red color quite easily with it, and she said that re-dying was much easier than with the dyes that salons use or that can be bought from department stores. Sorry I can't give any first-hand experience, I'm still in love with my natural color and so haven't tried anything else .
They do have special shampoos and conditioners that help preserve the color. Another thing you can do if you get it done professionally is, get heavy red highlights instead of coloring your whole head red. This way, when some it does start to fade, it will blend it better than if your whole head was red.
As well as using shampooes and conditioners, there are also serval different masks you could use to preserve the the colors. Try half and alvacado 1Tablespoon of honey 1 cup of regular non fat yougurt 1 teaspoon of cocunut milk or oil (this mask is also great for your face!) or take regular nonflavor coffee, when at room temp poor over your hair and leave in for 20-30minutes.