The best colours for a Sun umbrella will be—

The optimal design for a sun umbrella utilizes white on the top and black on the inside. White surfaces reflect the majority of incident solar radiation and heat, preventing the umbrella fabric from overheating and reducing the amount of thermal energy transferred to the person beneath. Conversely, a black interior is highly effective at absorbing radiation [1]. This is crucial because the ground and surrounding surfaces reflect sunlight and UV rays upward; a black underside absorbs these reflected rays rather than reflecting them back onto the user's face and body. While dark colors provide high UV protection by absorbing rays, they also trap heat. Therefore, the white-top/black-inside combination maximizes heat reflection from above while minimizing secondary radiation exposure from below, ensuring both cooling and protection.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > Why is it more comfortable to wear white or light-coloured clothes during summers and dark-coloured clothes during winters? > p. 96