To see a version that should have slightly more rapid alternation, try this, although this may be so fast that the that the leftward-tilted bars look muddy (unsaturated) instead of bright green as your display or your brain (depending on your display's temporal parameters) begin to blur the colors together.
**Note: the transparency/rivalry percept is sensitive to the speed and smoothness of the presentation and these depend on your particular computer and web browser configuration. The animation does not work well on LCD screens (such as laptop displays). If the animation is slow such that you experience first one pattern, then the other, or if the display seems to stutter or present one frame longer than another, then try quitting any other concurrently-running applications on your computer. Some of the rivalry in your display may be due to nonuniform presentation rate rather than mental fluctuations. For best results, it is recommended you download the movie files and view them with a quicktime movie player as the only application running.