int redCounter = 0;
int greenCounter = 0;
int yellowCounter = 0;

unsigned long previousMillis = 0;
const long interval = 500;

void setup() {
  pinMode(8, OUTPUT);
  pinMode(5, INPUT_PULLUP);

  pinMode(12, OUTPUT);
  pinMode(6, INPUT_PULLUP);

  pinMode(13, OUTPUT);
  pinMode(4, INPUT_PULLUP);

  Serial.begin(9600);
}

void loop() {
  if(digitalRead(5) == LOW) {//green
    digitalWrite(8, HIGH);
    delay(500);
    digitalWrite(8, LOW);

    greenCounter++;
    Serial.print("The Green LED was turned on ");
    Serial.print(greenCounter);
    Serial.println(" times.");
    }

  else if(digitalRead(6) == LOW) {//red
    digitalWrite(12, HIGH);
    delay(500);
    digitalWrite(12, LOW);

    redCounter++;
    Serial.print("The RED LED was turned on ");
    Serial.print(redCounter);
    Serial.println(" times.");
  }

  else if(digitalRead(4) == LOW) {//yellow
    digitalWrite(13, HIGH);
    delay(500);
    digitalWrite(13, LOW);

    yellowCounter++;
    Serial.print("The Yellow LED was turned on ");
    Serial.print(yellowCounter);
    Serial.println(" times.");
  }
}