int r = 2;
int g = 3;
int b = 4;
int port = 2;
int signal = 1;

void setup() {
  Serial.begin(9600);
  pinMode(r, OUTPUT);
  pinMode(g, OUTPUT);
  pinMode(b, OUTPUT);
}

void loop() {
  digitalWrite(port, signal);
  port += 1;
  if(port == 5) 
    port = 2;
    signal = signal ? 0 : 1;
  delay(100);

}