Police Style Strobe on an ATTiny

// police strobe sketch - PNP transistors control RGB LEDs with
// a common cathode. LOW = LED on, HIGH = LED OFF
//#include <Tone.h>

//  Tone siren;
  const int leftRedPin = 0;
  const int leftBluePin = 1;
  const int rightRedPin = 4;
  const int rightBluePin = 3;

void setup() {
  pinMode(leftRedPin, OUTPUT);
  digitalWrite(leftRedPin, HIGH);
  pinMode(leftBluePin, OUTPUT);
  digitalWrite(leftBluePin, HIGH);
  pinMode(rightRedPin, OUTPUT);
  pinMode(rightBluePin, OUTPUT);
//  siren.begin(4);

}

void loop() {
//  tone(4, 2000, 50);
  for (int i = 0; i <= 12; i++) {
    digitalWrite(leftRedPin, LOW);
    digitalWrite(rightBluePin, LOW);
    delay(30);
    digitalWrite(leftRedPin, HIGH);
    digitalWrite(rightBluePin, HIGH);
    delay(30);
  }
  delay(150);
  for (int i = 0; i <= 12; i++) {
    digitalWrite(leftBluePin, LOW);
    digitalWrite(rightRedPin, LOW);
    delay(30);
    digitalWrite(leftBluePin, HIGH);
    digitalWrite(rightRedPin, HIGH);
    delay(30);
  }
  delay(150);
}