#define LED1 2  // Red
#define LED2 3  // Green
#define LED3 4  // Blue

unsigned long led1Millis, led2Millis, led3Millis;
int led1Status = LOW, led2Status = LOW, led3Status = LOW;

void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  led1Millis = millis();
  led2Millis = millis();
  led3Millis = millis();
}

void loop() {
  if(GetTick() >= led1Millis) {
    if(led1Status == HIGH) {
      LED(LED1, LOW);
      led1Status = LOW;
    }
    else {
      LED(LED1, HIGH);
      led1Status = HIGH;
    }
    led1Millis = GetTick() + 1000;
  }
  if(GetTick() >= led2Millis) {
    if(led2Status == HIGH) {
      LED(LED2, LOW);
      led2Status = LOW;
    }
    else {
      LED(LED2, HIGH);
      led2Status = HIGH;
    }
    led2Millis = GetTick() + 2000;
  }
  if(GetTick() >= led3Millis) {
    if(led3Status == HIGH) {
      LED(LED3, LOW);
      led3Status = LOW;
    }
    else {
      LED(LED3, HIGH);
      led3Status = HIGH;
    }
    led3Millis = GetTick() + 500;
  }
}

void LED(int number, int status) {
  digitalWrite(number, status);
}

unsigned long GetTick() {
  return millis();
}