Science Question

i think there would be a brown or black paper appear

A red paper looks red. Because when white light falls on it, it reflects red light only but absorbed all other colours. So, if only green light falls on it, the green light would be absorbed by the red paper. No light is reflected to our eyes, the red paper looks black in colour.

white light is made up of red, orange, yellow, green, indigo, blue and purple lights.