The D'ni people used a visual color symbology. It was based on a 6-basic color system, represented as circular eyes. Obviously there were intermediate shapes between these "keys", indicating hue combinations. Gehn employed these symbols with his Fire-marble Domes. The circumference of each dome had a series of 36 symbols.[1]

The colors were:

  • Horizontal closed eye (a circle with a horizontal bar): Orange
  • Horizontal eye: Yellow
  • Fully opened eye (a circle with a dot): Green
  • Vertical eye: Blue
  • Vertical closed eye (a circle with a vertical bar): Purple
  • "Cat" eye: Red

Gehn, being obsessed with the number five, considered that the 6-color basis was superficial, and was attempting to determine if the symbology reflected the principle on five.[2] While assigning a color code to the Dome of each island, he left out Yellow, and assigned the rest to the five islands of Riven: Book Assembly Island (Purple), Prison Island (Blue), Temple Island (Green), Survey Island (Orange), Jungle Island (Red).