int led_R = 8;
int led_G = 9;
int led_Y = 10;
void setup() {
  pinMode((led_R), OUTPUT);
  pinMode((led_G), OUTPUT);
  pinMode((led_Y), OUTPUT);
}

void loop() {
  digitalWrite(led_R,1);
  digitalWrite(led_G,0);
  digitalWrite(led_Y,0);
  delay(1000);

  digitalWrite(led_R,0);
  digitalWrite(led_G,1);
  digitalWrite(led_Y,0);
  delay(1000);

  digitalWrite(led_R,0);
  digitalWrite(led_G,0);
  digitalWrite(led_Y,1);
  delay(1000);
}