What did you expect ? One pane filter all light except green, the other one filters all light except blue -> no light is left. The same would happen in real-life. If you want to mix two colors you will need two light sources.
Please attach screenshots instead of linking to an external site. Additionally the screenshots you linked are not blurry in any way.
What did you expect ? One pane filter all light except green, the other one filters all light except blue -> no light is left. The same would happen in real-life. If you want to mix two colors you will need two light sources.