Vibgyor+Debounce

const int buttonPin = 2;
int i=1;
const int redPin = 11;
const int greenPin = 10;
const int bluePin = 9;        
int buttonState;             
int lastButtonState = LOW;   
unsigned long lastDebounceTime = 0;  
unsigned long debounceDelay = 50;    

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);  
}

void loop() 
{
  int reading = digitalRead(buttonPin);
  if (reading != lastButtonState)
  {
    lastDebounceTime = millis(); // Reset the debouncing timer
  }
  if ((millis() - lastDebounceTime) > debounceDelay) // Check if state change has lasted for longer time than debounce delay
  {
    if (reading != buttonState) 
    {
      buttonState = reading;
      if (buttonState == HIGH) // Only shift if button is pressed
      {
        i++;
        if (i==8)
        {
          i=1;
        }
      }
   }
 }
 switch(i)
        {
        case 1:setColor(255, 0, 0);  // red
               break;
        case 2:setColor(255, 100, 0);  // orange
               break;
        case 3:setColor(255,255,0);  // yellow
               break;
        case 4:setColor(0, 255, 0);  // green
               break;
        case 5:setColor(0,0,255);  // blue
               break;
        case 6:setColor(75,0,130);  // indigo
               break;
        case 7:setColor(148,0,211);  // violet
               break;
       }
 lastButtonState = reading;
}

void setColor(int red, int green, int blue) // set RGB colour intensities
{
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);  
}