RGB LED by BARRAGAN http://barraganstudio.com

Demonstrates the use of PWM pins (analog output) to change the color of an RGB LED. On Wiring v1 boards the PWM capable pins are: 29, 30, 31, 35, 36 and 37 On Wiring S board the PWM capable pins are: 4, 5, 6, 7, 19 and 20

int REDPin = 4;    // RED pin of the LED to PWM pin 4
int GREENPin = 5;  // GREEN pin of the LED to PWM pin 5
int BLUEPin = 6;   // BLUE pin of the LED to PWM pin 6
int brightness = 0; // LED brightness
int increment = 5;  // brightness increment

void setup()
{
  pinMode(REDPin, OUTPUT);
  pinMode(GREENPin, OUTPUT);
  pinMode(BLUEPin, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
  brightness = brightness + increment;  // increment brightness for next loop iteration

  if (brightness <= 0 || brightness >= 255)    // reverse the direction of the fading
  {
    increment = -increment;
  }
  brightness = constrain(brightness, 0, 255);
  analogWrite(REDPin, brightness);
  analogWrite(GREENPin, brightness);
  analogWrite(BLUEPin, brightness);

  delay(20);  // wait for 20 milliseconds to see the dimming effect
}