Most camera bodies are black for a mix of practical, manufacturing, and marketing reasons. A dark exterior reduces unwanted reflections, which can matter in controlled lighting or studio work where a bright camera body could act like an uncontrolled reflector. Black is also a common, durable, and inexpensive finish: black pigments are cheap, resist fading, and can help protect plastics from UV degradation. Black is also a safe, widely accepted product color.

Large white telephoto lenses are a different case. Their size gives them much more surface area exposed to sun, and the lighter finish helps reflect more heat, including infrared, reducing internal temperature rise. That’s why some long lenses are white even though most bodies are not.

Yes, excessive heat can be harmful to cameras, cards, and mechanical components. If your gear is becoming very hot in direct sun, using shade or a light-colored cover is sensible. Also, a white surface does not automatically feel cooler to the touch; the material and how it transfers heat matter too.