void setup() {
  pinMode( 8, OUTPUT); //Blauw
  pinMode( 9, OUTPUT); //Groen
  pinMode(10, OUTPUT); //Red
}

void loop() {
  int pauseMS = 500;
  for(int pinNumber = 8; pinNumber <= 10; pinNumber = pinNumber + 1) {
    digitalWrite(pinNumber, HIGH);   // turn the led on
    delay(pauseMS);             // wait for a second
    digitalWrite(pinNumber, LOW);   // turn the led off
    delay(pauseMS);             // wait for a second
  }
}