I want to share this modification to the RGB tutorial since it was fun and looks nice. This RGB LED which came with the Adafruit ARDX kit is actually just a packaging of 3 LEDs sharing a common lead on one side. Controlling it is (almost) exactly the same as controlling 3 separate LEDs. It’s important to note that this particular RGB LED is common anode(+) which in the end means that unlike the other tutorials, 5V ==> Off; 0V ==> Max brightness.
Anyway here is some code that continuously and smoothly runs the LED through a (basically) non-repeating spectrum. It’s not random but it will appear random to the human eye. Importantly, the steps are smooth so there are no sudden shifts in color or brightness.