The first pictures in these posts show what the lights look like without any filament in front of them. In the second photo, you see these red, blue, green lights covered by a yellow, magenta, and red filament. The green light now looks cyan now because blue and yellow make cyan. The green light now doesn't show because it is covered by a magenta filament and green and magenta absorb each other. The red light still looks red because it is covered by a red filament which does nothing to the light passing through.