int red=10;
int yellow=9;
int green=8;
void setup() 
{
pinMode(red,OUTPUT);
pinMode(yellow,OUTPUT);
pinMode(green,OUTPUT);
Serial.begin(9600);
}

void loop()
 {
digitalWrite(red,HIGH);
Serial.println("red is on");
digitalWrite(red,LOW);
delay(1000);
digitalWrite(yellow,HIGH);
Serial.println("yellow is on");
digitalWrite(yellow,LOW);
delay(1000);
digitalWrite(green,HIGH);
Serial.println("green is on");
digitalWrite(green,LOW);
delay(1000);
}