int red=2;
int blue=3;
int yellow=4;
int green=5;

void setup() {
  pinMode(red, OUTPUT);
  pinMode(blue, OUTPUT);
  pinMode(yellow, OUTPUT);
  pinMode(green, OUTPUT);
  // put your setup code here, to run once:

}

void loop() {
  digitalWrite(red, HIGH);
  delay(300);
  digitalWrite(red, LOW);
  digitalWrite(blue, HIGH);
  delay(300)
  digitalWrite(blue, LOW);
  digitalWrite(yellow, HIGH);
  delay(300);
  digitalWrite(yellow, LOW);
  digitalWrite(green, HIGH);
  delay(300);
  digitalWrite(green, LOW);

  // put your main code here, to run repeatedly:

}