int red=6;
int green=2; 
int yellow=3;

void setup() {
  // put your setup code here, to run once:
pinMode(6,OUTPUT);
pinMode(3,OUTPUT);
pinMode(2,OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(red,HIGH);
  delay(15000);
 Serial.print("stop");
digitalWrite(red,LOW);
 
digitalWrite(yellow,HIGH);
  delay(15000);
 Serial.print("wait");

digitalWrite(yellow,LOW);

digitalWrite(green,HIGH);
  delay(15000);
 Serial.print("GO");
digitalWrite(green,LOW);
  
}