Diodes are electrical devices that allow electricity to flow in one direction but not in the reverse direction, It was discovered, quite by accident, that certain kinds of diodes would emit light. Now LEDs are everywhere---from indicators on electronic equipment to traffic lights. They require very little power, can produce any color and have an extremely long life. They also can be switched on and off very quickly, which makes them perfect for panels whose only purpose is to produce interesting patterns of light.
Dance clubs are a natural place to see some great RGB LED effects. The most important control on these panels is the speed knob, which controls how fast the lights change from one pattern to the next. When the time change is set to match the rhythm of the beats of a song, the lights appear to be responding to the music. It is inevitable that some color sequence will match some melodic lines, which only enhances the illusion. "Movement" is achieved by making a pattern repeat across the panel but shifted over one column on each change. This makes it look like the pattern is moving across the panel. Another common effect is created by starting with one color that is shown on just the outermost lights, and then turning these off and lighting the next innermost rows and column and so forth until the middle of the panel is illuminated, making the pattern appear to be moving inward or away. Reversing the process makes it look like the lights are exploding outward.
The easiest place to see a lot of RGB LED effects is on YouTube---there are thousands of examples. Of course, they are much more impressive in person. Some arched walkways now have ceilings that feature RGB LED displays, which can sometimes slow down pedestrian traffic. The "movement" of lights in these hallways is almost always toward the direction you should be moving---if the traffic is one-way---because otherwise it could confuse pedestrians. One of the most impressive displays is the "rainbow effect," in which the rows are set to the colors of a rainbow and then shifted one row at a time, making the rainbow seem to ripple overhead.