So you have seen these color filters (or gels as they are also called). When you look through a red filter, everything looks red. What do they do to the light? I am not going to tell you the answer. However, I will show you some examples so that you can figure out the answer yourself. In this video, I am going to use a red and a green laser pointer. The nice thing about laser pointers is that they essentially create only one color of light.