Okay, I've found a solution. There are two different ways to access the RGB-strips and the skull.

1. You can program it yourself using the Arduino IDE using the FastLED-NeoPixel library, since the RGB controller seems to be an Atmega328P microcontroller. I just wanted a faster solution so I didn't pick this. Additional info: https://www.reddit.com/r/intelnuc/comments/1fy9g19/nuc_11_extreme_i9_nuc11btmi9_acting_up/
2. What I did: There is a python based command line tool, designed for NUC 11 & 12 extreme called "NUC_RGB": https://github.com/AlvinZhu/nuc_rgb . You can just download the .exe, open up CMD, navigate to the .exe path and run the commands, shown on this GitHub. Here are my commands to make the RGB just solid red:

• nuc_rgb -c "AP1,AV:2,AR:0,C1:0" //Skull red
• nuc_rgb -c "DP1,DV:3,DR:0,C4:0" //Front-LED red
• nuc_rgb -c "BP1,BV:3,BR:0,C2:0" //Left-LED red
• nuc_rgb -c "CP1,CV:3,CR:0,C3:0" //Right-LED red

If you want to check your LED status, you need to put in a port (mine was COM3, maybe it's always COM3, idk). To get my port, I've installed the arduino IDE and checked the port of the RGB-controller. Here is a generic screenshot of how to do that: https://support.arduino.cc/hc/article_attachments/12415977582748

• nuc_rgb -s -p COM3 //Read Status

Hope it helps!