Am sure most know this, but I remember when my Mom reminded me to always turn dark items inside out when line drying in the sun, because this prevents fading.
On the other side of the coin, the sun does a great job of bleaching whites. I have had some T shirts with tomato stains(canning I am sure) that I have left out a day (or longer if I am busy) & they come out SO BRIGHT!
I dry my light clothes outside in the sun and my darks under my porch on a retractable clothes line. I LOVE my retractable clothes line and you can find them on-line really cheap.