const int LED1 = 1; // PB1
const int LED2 = 0; // PB0

void setup() {
  pinMode(LED1, OUTPUT); // LED_YEL
  pinMode(LED2, OUTPUT); // LED_BLU
}

void SetColour (int colour, int intensity) {
  analogWrite(colour, intensity);
}
void loop() {
  for (int i = -255; i <= 254; i++) {
    SetColour(LED1, abs(i));
    SetColour(LED2, 255 - abs(i));
    delay(2); 
  }
}