I got tired of TCD (Ternary Coded Decimal) as you have to remember that there is an implicit digit separator before the 5th LED from the right. So I added pure ternary encoding.

The top 6 LEDs display the hour, 2 LEDs per trit. Each trit is encoded by 0 = OFF-OFF, 1 = OFF-RED, 2 = YELLOW-OFF. Reading from left to right, the value of each LED is:

18, 9, 6, 3, 2, 1

The bottom 8 LEDs display the minute, 2 LEDs per trit. Each trit is encoded by 0 = OFF-OFF, 1 = OFF-RED, 2 = GREEN-OFF. Reading from left to right, the value of each LED is:

54, 27, 18, 9, 6, 3, 2, 1

All that was needed in the firmware was another assembly-time option, and another lookup table. I had to move and change some of the LEDs on the existing display board. I could have made another display board, but I don't intend to continue using the TCD display.

It'll take a while to get used to reading ternary.