#define LEDY 19 // yellow LED
#define LEDG 18 // green LED
#define LEDR 23 // red LED
#define PB1 27 // green button
#define PB2 25 // blue button

void setup()
{
  Serial.begin(115200);
  Serial.println("Blink program started");
  pinMode(LEDR,OUTPUT);
  pinMode(LEDG,OUTPUT);
  pinMode(LEDY,OUTPUT);
  pinMode(PB1, INPUT);
  pinMode(PB2, INPUT);
  digitalWrite(LEDY,HIGH); // ensure that the yellow LED remains off
}

void loop() // states the 4 possibilities
{ // put your main code here, to run repeatedly:
  if (digitalRead(PB1) == 0 && digitalRead(PB2) == 0) // press both buttons
  { // both lights are on
    digitalWrite(LEDR,LOW);
    digitalWrite(LEDG,LOW);
  }

  if (digitalRead(PB1) == 1 && digitalRead(PB2) == 0) // pressed the blue button
  { // one is on while the other is off
    digitalWrite(LEDR,HIGH);
    digitalWrite(LEDG,LOW);
  }

  if (digitalRead(PB1) == 0 && digitalRead(PB2) == 1) // pressed the green button
  { // one is on while the other is off
    digitalWrite(LEDR,LOW);
    digitalWrite(LEDG,HIGH);
  }

  if (digitalRead(PB1) == 1 && digitalRead(PB2) == 1) // pressed none of the buttons
  { // both lights are off
    digitalWrite(LEDR,HIGH);
    digitalWrite(LEDG,HIGH);
  }
}