Connect the cathode (the longest leg) of the Tri-color LED to Pin 6 GND.

[JeepNL]

About: Windows-iotcore-samples/Samples/RGBLED/

README: "Connect the cathode (the longest leg) of the Tri-color LED to Pin 6 GND."

I'm using a Raspberry 3B+. Where does the led get its power from?

I've connected the longest leg to 3.3V (not to GND) and then it sort of works. But (example) the blue led goes ON when I use ".Low"

redpin.Write(GpioPinValue.High);
greenpin.Write(GpioPinValue.High);
bluepin.Write(GpioPinValue.Low);

I'm using this in a Windows 10 IoT Background Service and when the program is not running the RGB led shines a little bit of blue light. When I set all the pins to HIGH, when the program runs, the led turns completely off.

[JeepNL]

Okay, there are Cathode & Anode RGB Leds. Didn't know that. Got it to work. Even with PWM (lightning)