Here's why:

* Clouds are made of water droplets or ice crystals. These tiny particles scatter and reflect light in all directions.

* The amount of reflection depends on the size and density of the cloud particles. Thicker, denser clouds reflect more sunlight, which is why they appear white or gray.

* The angle of the sun also plays a role. Sunlight hitting a cloud at a low angle (like during sunrise or sunset) can cause the cloud to appear red or orange due to the scattering of longer wavelengths of light.

This is why clouds can appear so bright and sometimes even block the sun's light.