int LEDblue = 6;
int LEDred = 3;
int potPin = A0;
int potVal = 0;

void setup() {
  pinMode(LEDblue, OUTPUT);
  pinMode(LEDred, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  potVal = analogRead(potPin);
  Serial.println(potVal);

  if (potVal >= 100 && potVal <= 500) 
  {
    int blueBrightness = map(potVal, 100, 500, 0, 255);
    analogWrite(LEDblue, blueBrightness);
    analogWrite(LEDred, 0);
  } else if (potVal >= 600 && potVal <= 1000) {
    int redBrightness = map(potVal, 600, 1000, 255, 0);
    analogWrite(LEDred, redBrightness);
    analogWrite(LEDblue, 0);
  } //else {
    //analogWrite(LEDblue, 0);
   // analogWrite(LEDred, 0);
  //}
}