const int red=11;
const int yellow=10;
const int green=9;
const int blue=8;
const int key=7;

void setup() {
  pinMode(red, OUTPUT);
  pinMode(yellow, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(blue, OUTPUT);
  pinMode(key, INPUT);
}

void loop() {
      for (int i=blue; i<=red; i++) {
        if (digitalRead(key)) {
          i--;
        }
          digitalWrite(i, 1);
          delay(200);
          digitalWrite(i, 0);
      }
      for (int i=red; i>=blue; i--) {
        if (digitalRead(key)) {
          i++;
        }
        digitalWrite(i, 1);
        delay(200);
        digitalWrite(i, 0);
      }
    }