int red_pin = 6;
int grn_pin = 5;
int blu_pin = 3;

int ldr_pin = A0;
int ldr_val;

unsigned long currentTime, lastTime;
bool rgbState; // for red and blue only

void setup() {
  pinMode(red_pin, OUTPUT);
  pinMode(grn_pin, OUTPUT);
  pinMode(blu_pin, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  currentTime = millis();
  ldr_val = analogRead(ldr_pin);
  // Serial.println(ldr_val);

  if (ldr_val < 400) { // there is light
    if (currentTime - lastTime > 500) {
      rgbState = !rgbState;
      lastTime = currentTime;
    }

    if (rgbState == true) {
      red();
      Serial.println("Red");
    }
    else {
      blue();
      Serial.println("Blue");

    }
  }
  else {
    green(); 
    Serial.println("Green");
  }
}

void red() {
  analogWrite(red_pin, 255);
  analogWrite(grn_pin, 0);
  analogWrite(blu_pin, 0);
}

void green() {
  analogWrite(red_pin, 0);
  analogWrite(grn_pin, 255);
  analogWrite(blu_pin, 0);
}

void blue() {
  analogWrite(red_pin, 0);
  analogWrite(grn_pin, 0);
  analogWrite(blu_pin, 255);
}