const int RED_PIN = 8;
const int GREEN_PIN = 0;

void setup() {
  // put your setup code here, to run once:
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(RED_PIN, HIGH); //5v
  digitalWrite(GREEN_PIN, LOW);
  delay(1000); //ms
  digitalWrite(RED_PIN, LOW); //0v
  digitalWrite(GREEN_PIN, HIGH);
  delay(1000);
}