unsigned long init_time = millis();
unsigned long curr_time;
unsigned long time_diff;
String color = "Red";

void setup() {

}

void loop() {
  curr_time = millis();
  time_diff = curr_time - init_time;

  if (color == "Red") {
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);

    analogWrite(10, 0);
    analogWrite(11, 127);
    analogWrite(12, 255);
    
    if (time_diff >= 5000) {
      color = "Green";
      init_time = millis();
    }
  }
  else if (color == "Green") {
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, HIGH);

    analogWrite(10, 255);
    analogWrite(11, 255);
    analogWrite(12, 255);
    
    if (time_diff >= 5000) {
      color = "Yellow";
      init_time = millis();
    }
  }
  else if (color == "Yellow") {
    digitalWrite(2, LOW);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);

    analogWrite(10, 0);
    analogWrite(11, 127);
    analogWrite(12, 255);
    delay(250);
    analogWrite(10, 0);
    analogWrite(11, 0);
    analogWrite(12, 0);
    delay(250);

    if (time_diff >= 2000) {
      color = "Red";
      init_time = millis();
    }
  }
}