Sunlight causes colours to fade as it contains Ultraviolet Radiation (UV). Due to longer days in summer, clothes would tend to fade more. Clothes will tend to fade when you are drying them outdoors apart from just wearing them. Even though there is not much you can do to reduce fading there are a few handy tricks to keep in mind.
You can turn your clothes inside out when you put them out to dry. If you have a fixed clothesline then you would know the direction of the sunlight. Put the darker clothes further away from direct sunlight. We recommend you do not keep the darker clothes out longer than it takes to dry them. In summer, clothes would generally dry in about 30 minutes.