RGB LED on pins 3, 5 and 6, on an Arduino Uno

// RGB LED: red, green, blue, white and purple, a second each.
//
//   pin 3 -> 220 ohm -> red leg
//   pin 5 -> 220 ohm -> green leg
//   pin 6 -> 220 ohm -> blue leg
//   the long leg (the common cathode) -> GND
//
// An RGB LED is three LEDs in one lens. analogWrite() sets each one's
// brightness from 0 to 255 by switching the pin on and off very fast (PWM),
// and the eye mixes the three into one color. Pins 3, 5 and 6 can all do PWM.

const int RED_PIN = 3;
const int GREEN_PIN = 5;
const int BLUE_PIN = 6;

void setColor(int red, int green, int blue);

void setup() {
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: RGB LED, red 3, green 5, blue 6");
}

void setColor(int red, int green, int blue) {
  analogWrite(RED_PIN, red);
  analogWrite(GREEN_PIN, green);
  analogWrite(BLUE_PIN, blue);
}

void show(const char *name, int red, int green, int blue) {
  setColor(red, green, blue);
  Serial.println(name);
  delay(1000);
}

void loop() {
  show("red", 255, 0, 0);
  show("green", 0, 255, 0);
  show("blue", 0, 0, 255);
  show("white", 255, 255, 255);
  show("purple", 170, 0, 255);
}