A little out of focus but it’s working!
I didn’t change your code, just copied it right into Spark Dev and programmed the Core I had sitting next to me.
I just used a 100 ohm for RED, and a jumper for GREEN and BLUE.
RED measures 10mA, and GREEN and BLUE both measure 12mA.
Green is REALLY bright naturally to the eye, so that probably needs to be turned down a bit. Experiment with resistors there until you get the right blend.
The long pin of the RGB LED is Common Anode and I hooked it to 3V3 on the Core.
Hopefully you can figure out what is wrong with yours based on this 