int pot = A0;
int LEDr = 13;
int LEDg = 12;
int LEDb = 11; 
void setup() {
  // put your setup code here, to run once:
pinMode(pot, INPUT_PULLUP);
pinMode(LEDr, OUTPUT);
pinMode(LEDg, OUTPUT);
pinMode(LEDb, OUTPUT);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
int val_pot = analogRead(pot);
Serial.println(val_pot);

switch(val_pot) {
  case 0 ... 341:
    digitalWrite(LEDr, HIGH);
    digitalWrite(LEDg, LOW);
    digitalWrite(LEDb,  LOW);
  break;
  case 342 ... 684:
    digitalWrite(LEDr, HIGH);
    digitalWrite(LEDg, HIGH);
    digitalWrite(LEDb, LOW);
  break;
  case 685 ... 1023:
    digitalWrite(LEDr, LOW);
    digitalWrite(LEDg, HIGH);
    digitalWrite(LEDb, LOW);
  break;
 }
}