Eventually hair color will begin to fade. A trick to combat this without a re-color involves water, vinegar and lavender oil.
I suggest the following be done on clean hair:
Combine 1 cup cold water, 1 cup distilled vinegar (available at the grocery store) and a few drops of lavender oil (to counter the smell of the vinegar).
The acidity in the vinegar will super close the cuticle leaving you with the shiniest hair ever!