int led_red = 13;
int led_grn = 12;
int led_blu = 11;
void setup() {
  // put your setup code here, to run once:
pinMode(led_red, OUTPUT);
pinMode(led_grn, OUTPUT);
pinMode(led_blu, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(led_red, HIGH);
digitalWrite(led_grn, HIGH);
delay(500);
digitalWrite(led_red, LOW);
digitalWrite(led_grn, LOW);
delay(500);

digitalWrite(led_red, HIGH);
digitalWrite(led_grn, LOW);
delay(500);

digitalWrite(led_red, LOW);
digitalWrite(led_grn, LOW);
delay(500);

digitalWrite(led_red, LOW);
digitalWrite(led_grn, HIGH);
delay(500);

}