On the Subject of Hidden Colors

Each button on the module represents a color. While the right LED is unlit, pressing a button will show its color on the display.

Pressing the green button will switch on the LED, allowing you to press a button to solve the module. Pressing an incorrect button will cause a strike and switch off the LED.

Be sure to keep note of the button colors before the LED is switched on!

Pressing a button will highlight its number on the side display. The buttons are ordered from 1 to 20 starting from the top-left and going in reading order.

The color of the LED determines which buttons are named "A", "B", "C", "D", "E" and "F". Use the following table to find the correct buttons to use:

LED Color:
Red: Blue: Green: Yellow:
A X X X B X X E X X X X X X X X A X F X
X E X X X X X D X F X C A E X X X E X X
X X X F X X X C X A X B F D X X B X D X
C X X X D X X B X X X X X X X X X C X X
Orange: Purple: Magenta: White:
X X X X X X X X X X X X F X X A B X X X
D X X X X A B X D E X X X X X X X C X X
E A X X X C X X X F X X X X X X X D X X
F B C X X X X X X X E D C B A F E X X X

Now that you've identified which buttons to use, follow this table and stop at the first rule that applies:

Rule: Button:
Buttons A, B and C share the same color 4
Buttons D, E and F share the same color 9
The LED shares its color with buttons 1 and 20 14
Buttons 4, 8 and 16 share the same color 5
Button A shares its color with buttons 13 and 14 11
Button E is purple 17
There is an unlit CLR indicator 12
There is a lit TRN indicator 3
There are 6 or more batteries 8
Button C is orange or white 10
Button F is red or blue 6
Button B is not orange, magenta, purple or white 2
The LED doesn't share its color with buttons A, B, C, D, E and F 18
The first digit of the serial number is less than 3 1
Button E shares its color with the LED 19
The last digit of the serial number is prime 20
Button A is magenta, green or yellow 7
The LED shares its color with button C, E or F 15
Button C and D do not share the same color 13
If no previous rules applied 16

Some things are just hidden in plain sight.