@stargaze if you use semi permanent color try adding a little into your daily shampoo and conditioner. there's also a product by pravana called silk shine degrees. its a deep conditioner designed to seal the hair shaft and keep vibrant colors from fading. I used it on a client that had color that would fade in days, after a treatment her color lasted until about the time her roots grew out.
When I first started coloring my hair I slept with the semi color on overnight, wrapped in one of those small towels with the button on the back. That helped a lot, and retouching your color, before it needs it, will keep it brighter longer in the long run.