Here are the instructions.
Instructions to change colors on the speedo/tach combo
The trick with changing the colors is to get the unit into the right screen. Hopefully you have the written instructions.
Follow the steps in the instructions to toggle through the different displays such as COLOR ALL, LCD, DIAL, SPEEDO (NEEDLE COLOR) OR TACH (NEEDLE COLOR). Once you choose the color display function (LCD, speedo, etc.) and it is displayed on the screen you then quickly turn off the ignition switch and then immediately turn it to ACCY. Now the gauge will display the present color of that function.
Now this is where things get a bit confusing (as it did for me); pay attention. Press in and hold the trip set button. You continue to hold it and the colors will gradually change. As you hold the button in, it will cycle through the color rainbow and then you can release the trip set button at the color you desire.
The display will show the color number and you can write it down if you want to use it on another gauge component such as the tach, speedo, LCD screen, etc. Once you have the color selected you quickly turn off the ignition and then back to ACCY. This saves your color setting and returns you to continue with changing colors on other gauges. When done adjusting the colors, turn off the ignition. You're done!
I hope this helps. If this doesn't help you PM me.
If you don't have the written instructions, let me know.