<code C>
#include <stdio.h>
char incomingByte = 0;   // for incoming serial data
String inputStr = "";
int R,G,B;
boolean com = false;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(13,OUTPUT);
  pinMode(3,OUTPUT);
  pinMode(5,OUTPUT);
  pinMode(6,OUTPUT);
  analogWrite(3,255);
  analogWrite(5,255);
  analogWrite(6,255);
  inputStr.reserve(200);
}

void loop() {
  if (com == true)
  {
    sscanf(inputStr.c_str(), "R%dG%dB%d",&R,&G,&B);
    Serial.print("R:");
    Serial.print(R);
    Serial.print("  G:");
    Serial.print(G);
    Serial.print("  B:");
    Serial.println(B);
    analogWrite(3,255-R);
    analogWrite(5,255-G);
    analogWrite(6,255-B);
    
    com = false;
    inputStr = "";
  }
}

void serialEvent(){
//statements
  incomingByte = Serial.read();
  inputStr += incomingByte;
  if (incomingByte == '\n')
    com = true;
}
</code>