Find the correct 5-color code using numeric and colored hints.
Press Submit while the colored buttons display an incorrect color code
Step 1: Identify the correct color code
The 5 colored buttons can be clicked to toggle their color. They always cycle between the same colors in the same order. Pressing Query will cause two colored numbers to appear on the readout. The colored buttons and Query can be pressed as many times as you want.
Configure the colored buttons in any manner of your choosing (it is recommended to start with the default, all-white), then press Query until the readout displays numbers that are colored in some combination of green and magenta (e.g. greengreen or magentagreen).
If the rightmost number is green, subtract the number of unlit indicators from it. Otherwise, subtract the last number in the Serial #. The result is the number of correctly colored buttons.
Change the colors in a manner of your choosing, then repeat the above process. Continue until there are 5 correctly colored buttons, and then press Submit.
Changing one colored button one color at a time for each time you repeat the above process is a reasonable approach.
If you have all of the colored buttons set to the same color, and the number of correct colored buttons is calculated to be 0, then you might also try switching them all to the next color rather than one at a time (since you know in that case that there are no buttons required to be that color at all). Trying to alter multiple buttons at once except in that specific situation can be dangerous, because if the number of correct colors changes, you won't know which button(s) changed to the correct value(s), and you will likely have to perform redundant queries.
There are other combinations of number colors not listed here which could also be memorized. Green and magenta were selected because, when combined, the left number becomes entirely irrelevant (other than it needing to be one of those two colors). A close runner-up color pair is blue and white, which shares the property of ignoring the left number's color (although in their case, you use the left number for calculations, which makes them very slightly less intuitive to use). There are further color pairs which could be memorized- really, any color pair in the original manual's table which includes 'A' but not 'B' or 'C' will work, and there are many of these- but the previously mentioned two color pairs are the only ones that can ignore the left number's color. For any other pair, their positioning matters, and changes what you have to memorize. Of course, the more of these you memorize, the faster on average you can solve the module; but if you try to memorize all color combinations which meet the conditions specified, you've nearly almost memorized the entire table anyway.