int RED = 11;    // RED pin of the LED to PWM pin 9
int GREEN = 10;  // GREEN pin of the LED to PWM pin 10
int BLUE = 9;   // BLUE pin of the LED to PWM pin 11

int DELAY_TIME = 10;  //changes speed of fading
int MAX_BRIGHT = 255; //sets maximum brightness, 255 max brightness
int COLOR_MIX = 0; //variable to change the colors that are mixed in switch statement

void fade_in(int x) //loop that gradually turns the LED on using PWM
{
    int counter;

    for(counter = 0; counter < x; counter++)
    {
        led_mixer(COLOR_MIX, counter);
        delay(DELAY_TIME);
    }
}

void fade_out(int x) //loop that gradually turns the LED off using PWM
{
    int counter;

    for(counter = x; counter > 0; counter--)
    {
        led_mixer(COLOR_MIX, counter);
        delay(DELAY_TIME);
    }
}

void led_mixer(int color, int x) //uses switch statement to mix color combinations
{
    switch(color)
    {
      case 0:
        analogWrite(RED, x);
        analogWrite(GREEN, x);
        break;
      case 1:
        analogWrite(GREEN, x);
        analogWrite(GREEN, x);
        analogWrite(RED, x);
        break;
      case 2:
        analogWrite(RED, x);
        break;
    }
}

void setup()
{
  // nothing for setup
}

void loop() //loop forever
{
  fade_in(MAX_BRIGHT); //gradually turn the LED on to max brightness
  fade_out(MAX_BRIGHT); //gradually turn off the LED
  COLOR_MIX++; //increment to the next color combination

  if(COLOR_MIX == 7) //if all color combinations have been displayed, reset the cycle
  {
    COLOR_MIX = 0;
  }
}