int b = 11;
int r = 12;
int g = 13;
char incomingByte = 0;
int user_input = 0;

void setup()
{
  Serial.begin(9600);
  pinMode(b, OUTPUT);
  pinMode(g, OUTPUT);
  pinMode(r, OUTPUT);
}
void blue ()
{
  digitalWrite(b, HIGH);
  delay(1000);
  digitalWrite(b, LOW);
  delay(1000);
}

void green()
{
  digitalWrite(g,HIGH);
  delay(1000);
  digitalWrite(g,LOW);
  delay(1000);
}

void red ()
{
  digitalWrite(r,HIGH);
  delay(1000);
  digitalWrite(r,LOW);
  delay(1000);
}

void loop()
{
  Serial.println("1 - blue\n2 - green\n3 - red\n");
while(!Serial.available()) //while Serial communication is not active...
{}//do nothing
user_input = Serial.parseInt(); //store user's choice
switch(user_input) //according to user's input, a case will be activated
{
  // do something different depending on the input value:
case 1: // the user chose 1
Serial.println("blue led must turn on");
blue ();
break;
case 2: // the user chose 2
Serial.println("green led must turn on");
green ();
break;
case 3: // the user chose 3
Serial.println("red led must turn on");
red () ;
break;
}
delay(1000);
}