RGB Arduino remote code

remote.pde

int red = 11, green=10, blue=9, white=6;
String tempString=String(100), readString = String(100);

void setup() {
  pinMode(red, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(blue, OUTPUT);
  pinMode(white, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  tempString = readString;
  if (Serial.available()) {
    delay(10);
    readString = "";
    while (Serial.available() > 0) readString += (char) Serial.read();
  }
  if (readString!="" && readString!=tempString) progress(readString);
}

int pos(String s) {
  int l = s.length();
  for (int i=0; i<l; i++) {
    char c = s.charAt(i);
    if (c==':') return i;
  }
  return -1;
}

String substr(String s, int istart, int istop) {
  String b = "";
  int l = s.length();
  for (int i=istart; i<istop; i++) {
    char c = s.charAt(i);
    b = b+c;
  } return b;
}

void progress(String s) {
  String color = substr(s, 0 , pos(s));
  char buf[12]; // "-2147483648\0"
  String cmd = substr(s, pos(s)+1 , s.length());
  cmd.toCharArray(buf,12);
  int value =   atoi( buf );
  if (color=="r") analogWrite(red, value);  
  if (color=="g") analogWrite(green, value);  
  if (color=="b") analogWrite(blue, value);  
  if (color=="w") analogWrite(white, value);  
  if (color=="fn" && cmd=="red") {
     analogWrite(white, 0); 
     analogWrite(blue, 0);  
     analogWrite(green, 0);
     analogWrite(red, 255);
     delay(1000);
     analogWrite(red, 0);
     delay(1000);
  }
  if (color=="fn" && cmd=="strobe") {
     analogWrite(red, 255);
     analogWrite(blue, 255);  
     analogWrite(green, 255);
     analogWrite(white, 255);
     delay(100);
     analogWrite(red, 0);
     analogWrite(blue, 0);
     analogWrite(green, 0);
     analogWrite(white, 0);
     delay(100);
  }
  Serial.println(color+":"+buf);
}