//set colors to pins
const int RED_PIN = 9;
const int GREEN_PIN = 10;
const int BLUE_PIN = 11;

//time elapsed in milliseconds for spectrum
int DISPLAY_TIME = 10;

//setup output terminals
void setup()
{
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
}

//Indefinitely loop color functions
void loop()
{
  mainColors();
  showSpectrum();
}

//display primary and secondary colors one second each
 void mainColors()
 {
    digitalWrite(RED_PIN, LOW);
    digitalWrite(GREEN_PIN, LOW);
    digitalWrite(BLUE_PIN, LOW);
    delay(1000);

    digitalWrite(RED_PIN, HIGH);
    digitalWrite(GREEN_PIN, LOW);
    digitalWrite(BLUE_PIN, LOW);
    delay(1000);

    digitalWrite(RED_PIN, LOW);
    digitalWrite(GREEN_PIN, HIGH);
    digitalWrite(BLUE_PIN, LOW);
    delay(1000);

    digitalWrite(RED_PIN, LOW);
    digitalWrite(GREEN_PIN, LOW);
    digitalWrite(BLUE_PIN, HIGH);
    delay(1000);

    digitalWrite(RED_PIN, HIGH);
    digitalWrite(GREEN_PIN, HIGH);
    digitalWrite(BLUE_PIN, LOW);
    delay(1000);

    digitalWrite(RED_PIN, LOW);
    digitalWrite(GREEN_PIN, HIGH);
    digitalWrite(BLUE_PIN, HIGH);
    delay(1000);

    digitalWrite(RED_PIN, HIGH);
    digitalWrite(GREEN_PIN, LOW);
    digitalWrite(BLUE_PIN, HIGH);
    delay(1000);

    digitalWrite(RED_PIN, HIGH);
    digitalWrite(GREEN_PIN, HIGH);
    digitalWrite(BLUE_PIN, HIGH);
    delay(1000);
 }

//loop for spectrum display
 void showSpectrum()
 {
    int x;

    for(x = 0; x < 768; x++)
    {
      showRGB(x);
      delay(DISPLAY_TIME);
    }
 }

//function to determine intensity of colors for spectrum
void showRGB(int color)
{
  int redIntensity;
  int greenIntensity;
  int blueIntensity;

  if (color <= 255)
  {
    redIntensity = 255 - color;
    greenIntensity = color;
    blueIntensity = 0;
  }
  else if(color <= 511)
  {
    redIntensity = 0;
    greenIntensity = 255 - (color - 256);
    blueIntensity = (color - 256);
  }
  else
  {
    redIntensity = (color - 512);
    greenIntensity = 0;
    blueIntensity = 255 - (color - 512);
  }
  //display colors with determined intensities
  analogWrite(RED_PIN, redIntensity);
  analogWrite(GREEN_PIN, greenIntensity);
  analogWrite(BLUE_PIN, blueIntensity);
}