If you shine a beam of red light and a beam of green light on the same area of a screen, what color will you see on the screen?

At one end of the electromagnetic wave line, is the group o the visible spectrum. This is referred to as the visible light spectrum. The visible light with the shortest of the wavelength is the blue light and the one with the longest is the red light. 

The primary colors of the light spectrum are red, blue, and green. The combination of these colors will form other colors which are referred to as the secondary colors.

The combination of the beam of red light and the beam of green light will form yellow color.