char buffer[9];
int counter = 0;

void setup() {
 Serial.begin(9600);
}

void loop() {
  if (Serial.available() > 0) {
    char thisByte = Serial.read();
    buffer[counter] = thisByte;
    counter++;
    if (thisByte == '\n') {
     //Serial.println();
     parseBuffer();
     counter = 0;
    }
    //Serial.write(thisByte);
  }
}

void parseBuffer() {
  if (buffer[0] == 'R') {
   analogWrite(9, buffer[1]);
  }
  if (buffer[2] == 'G') {
   analogWrite(6, buffer[3]);
  }
  if (buffer[4] == 'B') {
   analogWrite(5, buffer[5]);
  }
  if (buffer[6] == 'Q') {
   analogWrite(3, buffer[7]);
  } 

}