What does it mean to use colored light to reflect the main body of things in photography? What does it mean to reflect things with light?

The question you asked is relatively large, which belongs to a theoretical problem with deep depth in photography. I can't speak clearly in a few words. Simply put, color, light, shadow, subject and so on are all terms in photography. Color is color, color, light is the angle and intensity of light, shadow is the light and shade effect produced by light, and the subject is the main thing to shoot, such as the protagonist in the novel. Photography is a plane art that expresses and reflects things through light and color. Through the difference between light and color, the plane picture has a three-dimensional effect. etc

I suggest you find some photography teaching materials online and learn some basic knowledge by yourself.