Yup I ll third or forth the "all of them" angle. While some colours will fade faster or be more noticeable, sunlight will with time bleach out just about everything. I would work to try and avoid as much direct contact with sunlight as you can
![Smile :)](https://mlparena.com/Smileys/default/smile_001.gif)
Or at least cycle ponies in and out of it. And be prepared for fading in any of those exposed unfortunately.