LEFT: It looks like a patch of green, but when you play the clip, you will see how that shade of green is reproduced on your TV. The green pixel (in each group of three) is hit with a strong jolt from the electron beam--and so it lights up brightly. But the beam pretty much skips the red and blue pixels, and so they are dim and don't contribute much.
RIGHT: The same phenomenon creates purple. Since purple is a combination of red and blue, both the red and blue pixels in each group of three are lit strongly by the electron beam. The green pixels are almost completely dark--since there is no green component in purple. Again, your TV can NOT reproduce purple, but when your eye and brain see a red dot right next to a blue dot, they are fooled into THINKING they see purple. It is on this foundation that color television is built.