Most white animals are just as vulnerable to the effects of the sun as humans. The absence of color which results in their white coat indicates that there is an absence of natural protection from the sun’s harmful UV rays.
An animal’s skin and fur’s natural color is what provides protection from the UV rays. The presence of melanin is the primary protector. If an animal does not have this naturally built in sunscreen they require protection from the sun, just like we do. They need to limit exposure or stay out of the sun.
Undomesticated animals often naturally avoid midday sun by coming out of the shade only in the late afternoon or evening. If you have a white pet it is best kept indoors.