The kind that absorb the rays are usually colorless. The physical sun screens that block the ultraviolet rays come in different colors. The sunscreens with the highest SPF many combine both agents that absorb and block the ultraviolet rays. Yes, clouds do not block ultraviolet rays. You do not have to be hot in order to be exposed to the harmful ultraviolet rays.
Tanning booths use ultraviolet A rays.
Ultraviolet A rays are less harmful than ultraviolet B rays but exposure to them in a tanning booth probably still increases your risk of skin cancer. African-Americans and other people with dark skin are at very low risk of skin cancer. They are naturally protected by the melanin, the dark pigment, in their skin. You can become allergic to sun screen. Skin cancer is very treatable, particularly when found early.