int rossoPin = 11;
int verdePin = 10;
int bluPin = 9;

void setup() {
  // put your setup code here, to run once:
pinMode(rossoPin, OUTPUT);
pinMode(verdePin, OUTPUT);
pinMode(bluPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
for(int i=0; i<256; i++){
rgb(255-i, i, 0);
delay(10);
}
for(int i=0; i<256; i++){
rgb(0, 255-i, i);
delay(10);
}
for(int i=0; i<256; i++){
rgb(i, 0, 255-i);
delay(10);
}
}

void rgb(int rosso, int verde, int blu){
analogWrite(rossoPin, rosso);
analogWrite(verdePin, verde);
analogWrite(bluPin, blu);
  }