const int buttonPinRed = 3;  
const int ledPinRed= 2;      

int buttonState = 0;      
int ledState = LOW;       

void setup() {
  pinMode(ledPinRed, OUTPUT);     
  pinMode(buttonPinRed, INPUT);   
}

void loop() {
  buttonState = digitalRead(buttonPinRed);  

  if (buttonState == HIGH) {   
    ledState = !ledState;      
    digitalWrite(ledPinRed, ledState);  
    delay(250);  
  }
}