#define R 3
#define G 6
#define B 5

void setup() {
  pinMode(R, OUTPUT);
  pinMode(G, OUTPUT);
  pinMode(B, OUTPUT);
}

void loop() {
  for (int i = 0; i<255; i++){
    analogWrite(R, 255-i);
    analogWrite(G, i);
    analogWrite(B, 0);
    delay(5);
  }
  for (int i = 0; i<255; i++){
    analogWrite(R, 0);
    analogWrite(G, 255-i);
    analogWrite(B, i);
    delay(5);
  }
  for (int i = 0; i<255; i++){
    analogWrite(R, i);
    analogWrite(G, 0);
    analogWrite(B, 255-i);
    delay(5);
  }
}