#define R 27
#define Y 26
#define G 25

void setup() {
  pinMode(R,OUTPUT);
  pinMode(Y,OUTPUT);
  pinMode(G,OUTPUT);
}

void loop() {
  digitalWrite(R,LOW);
  digitalWrite(Y,LOW);
  digitalWrite(G,HIGH);
  delay(3000);
  digitalWrite(R,LOW);
  digitalWrite(Y,HIGH);
  digitalWrite(G,LOW);
  delay(1000);
  digitalWrite(R,HIGH);
  digitalWrite(Y,LOW);
  digitalWrite(G,LOW);
  delay(2000);    //ms = 1/1000sec
}