int Red_LED = 8;
int Yellow_LED = 9;
int Green_LED = 10;
int Time_Delay = 500T;

void setup() {
  // put your setup code here, to run once:
  pinMode(Red_LED, OUTPUT);
  pinMode(Yellow_LED, OUTPUT);
  pinMode(Green_LED, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(Red_LED, HIGH);
  digitalWrite(Yellow_LED, HIGH);
  digitalWrite(Green_LED, HIGH);
  delay(Time_Delay);

  digitalWrite(Red_LED, LOW);
  digitalWrite(Yellow_LED, LOW);
  digitalWrite(Green_LED, LOW); 
  delay(Time_Delay);
}