Why can we see colors?
To be able to see an object, it is necessary to have a light source which emits light. This light rays are reflected from an object like a face and enter our eye. Only if an object is reflecting or emitting light, we can see the object. If you see different objects with different colors, it means that the object is absorbing some parts of the white light and reflect only a part of the original sun light.
Light Receiver - Our Eye
Light is everywhere in space and surrounds us continuously. We need light rays to observe our world. Without a light source it is not possible to see anything. Everything would be black around us. We can percept an object by receiving light through the lens of our eye. The light rays enters the inner of our eyes and hits some special cells. This special light sensitive cells are the rods & cones and forms the retina.