Working with Two LEDs

const int LED_red = 3;
const int LED_green = 6;

void setup() {
    pinMode (LED_red, OUTPUT);
    pinMode (LED_green, OUTPUT);
}

void loop() {
    for (int brightness=1; brightness<=255; brightness++)
    {
      analogWrite (LED_red, brightness);
      delay (5);
    }
    for (int brightness=255; brightness>0; brightness--)
    {
      analogWrite (LED_green, brightness);
      delay (5);
    }
    for (int brightness=255; brightness>0; brightness--)
    {
      analogWrite (LED_red, brightness);
      delay (5);
    }
    for (int brightness=1; brightness<=255; brightness++)
    {
      analogWrite (LED_green, brightness);
      delay (5);
    }
}