This change is called oxidation and is a gradual process, if you spend time outdoors, it could affect the natural appearance you're use to having with your hair piece.
Now other than staying inside all the time, not something I would want to do. We do carry products that will help protect your hair, like the BC Fibre Force line. You know what they say "an ounce of prevention, is a pound of protection!".
Another tip, is to consider wearing a hat especially when doing lawn work or playing that round of golf you've been dying to get into your schedule.
All of that being said, if it still happens you can certainly color your hair piece. I would suggest having us do it for you so you get the right shade or a licensed hairstylist. We have put together a great collection of hair care products for your shopping enjoyment. You will find a great deal of products with helpful ingredients designed to protect your hair piece from harmful UV Rays.