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

// RGB fade on pins 6, 5 and 3: red into green, green into blue, blue into red.
//
//   pin 6   the red leg, through 220 ohm
//   pin 5   the green leg, through 220 ohm
//   pin 3   the blue leg, through 220 ohm
//   the long leg (the common cathode) to GND
//
// An RGB LED is three small LEDs under one lens. analogWrite() sets each one
// from 0 (off) to 255 (full on), and your eye blends the three into a single
// color. Pins 3, 5 and 6 are all PWM pins, marked with a ~ on the board.
//
// The sketch hands the light from one color to the next: as one value falls
// from 255 to 0, the next rises from 0 to 255, so the total stays the same
// and the color walks all the way around the wheel.

const int RED_PIN = 6;
const int GREEN_PIN = 5;
const int BLUE_PIN = 3;
const int STEP_MS = 8;

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

// Cross-fade from `from` to `to`, leaving the third pin dark.
void handOver(int from, int to, const char *name) {
  for (int value = 0; value <= 255; value++) {
    analogWrite(from, 255 - value);
    analogWrite(to, value);
    delay(STEP_MS);
  }
  Serial.println(name);
}

void setup() {
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: RGB fade on pins 6, 5 and 3");
  show(255, 0, 0);
  Serial.println("red");
}

void loop() {
  handOver(RED_PIN, GREEN_PIN, "green");
  handOver(GREEN_PIN, BLUE_PIN, "blue");
  handOver(BLUE_PIN, RED_PIN, "red");
}