const int yellow =2;
const int red =3;
const int buttonpin=4;

void setup() {
  // put your setup code here, to run once:
pinMode(led, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(buttonpin, INPUT_PULLUP);


  // led1 ON at start
  digitalWrite(led1, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
  // Button pressed
  if (digitalRead(buttonPin) == LOW) {

    // Turn OFF led1
    digitalWrite(led1, LOW);

    // Turn ON led2
    digitalWrite(led2, HIGH);

    // Stay led2 for 3 seconds
    delay(3000);

    // Return to led1
    digitalWrite(led2, LOW);
    digitalWrite(led1, HIGH);
  }
}