#define RGB_R 11
#define RGB_G 10
#define RGB_B 9

int r=255;
int g=0;
int b=0;

void setup() {
  pinMode(RGB_R, OUTPUT);
  pinMode(RGB_G, OUTPUT);
  pinMode(RGB_B, OUTPUT);
}
void loop() {
  RGB_color(r--, 0, b++);
  if(r<0) r=255;
  if(b>255) b=0;
  delay(20);
}
void RGB_color(int red_light_value, int green_light_value, int blue_light_value)
 {
  analogWrite(RGB_R, red_light_value);
  analogWrite(RGB_G, green_light_value);
  analogWrite(RGB_B, blue_light_value);
}