Each "pixel" in this display is a sealed container of thick shatter-proof glass. It contains salt water, pH indicator, two electrodes, and a small spark plug.
To activate a pixel, current is applied across the electrodes. This will electrolyze the brine and change the pH of the solution:
==> H2(g)+Cl2(g) + 2NaOH (aq)
This will cause the indicator change colors (e.g., phenolpthalein turns purple when acidic, etc.)
Here's the fun part: To reset, the spark-plug (which is at the top of our chamber, and thus dry) is activated, causing the hydrogen and chlorine to react with each other (giving off light and sound):
H2(g) + Cl2(g) ==> 2HCl(g)
The gaseous hydrogen chloride then dissolves in the NaOH solution and yields:
HCl(aq) + NaOH(aq) ==> NaCl(aq) +H20(l)
This will restore the pH to neutral and re-set the original color of our "pixel"
WARNING: do NOT try this at home. A much simpler version might be an array of beakers filled with salt water (under a fume hood, of course). The "re-set" can be done with a little bit of HCl.