They are the same material; however the left side gets a clearcoat to protect its lettering. This grey color will show strikingly different shades based on the dominant light source's color temp. I had two identical panels next to each other, where one was directly underneath a halogen lamp, and the other in natural daylight - I swore they were two different colors, and I swapped them and they each reversed. Both sides are Acrycast (a brand of cast acrylic) in a color of grey they call HP504. You can see in the video at 6:25 that the left panel's left side is a strikingly different color than its very own right side (but it isn't).