#define GREEN 10 
#define RED 9
void setup() {
  // put your setup code here, to run once:
  pinMode(GREEN, OUTPUT);
  pinMode(RED, OUTPUT);
} 

void loop() {
  digitalWrite(GREEN, HIGH);
  delay(1000); // this speeds up the simulation

  digitalWrite(GREEN, LOW);
  delay(1000);

  digitalWrite(RED, HIGH);
  delay(1000); // this speeds up the simulation

  digitalWrite(RED, LOW);
  delay(1000);
}