void setup() {
  // put your setup code here, to run once:
  pinMode(15,OUTPUT);
  pinMode(2,OUTPUT);
  pinMode(4,OUTPUT);
}
int blue=15;
int red=2;
int green=4;
void display(int bluevalue,int redvalue,int greenvalue){
  analogWrite(blue,bluevalue);
  analogWrite(red,redvalue);
  analogWrite(green,greenvalue);
}
void loop() {
  
  for(int i=0;i<256;i++){
    display(255,i,0);
    delay(4);
  }
  for(int i=0;i<256;i++){
    display(255-i,255-i,i);
    delay(4);
  }
  for(int i=0;i<256;i++){
    display(0,i,255-i);
    delay(4);
  }
  for(int i=0;i<256;i++){
    display(i,255-i,0);
    delay(4);
  }
}