String ch;
int LED_Sarkans = 7;
int LED_Zals = 5;

void setup() {

  Serial.begin(9600);
  pinMode(LED_Sarkans, OUTPUT);
  pinMode(LED_Zals, OUTPUT);
}

void loop() {

  if(Serial.available()){

    ch = Serial.readString();
    ch.trim();
    if(ch=="S"){
      digitalWrite(LED_Zals, LOW);
      digitalWrite(LED_Sarkans, HIGH);
      Serial.println ("Sarkanais LED");
    }
    else if(ch=="Z"){
      digitalWrite(LED_Sarkans, LOW);
      digitalWrite(LED_Zals, HIGH);
      Serial.println ("Zaļais LED");
    }
    else if(ch=="ON"){
      digitalWrite(LED_Sarkans, HIGH);
      digitalWrite(LED_Zals, HIGH);
      Serial.println ("Abi LED");
    }
    else if(ch=="OFF"){
      digitalWrite(LED_Sarkans, LOW);
      digitalWrite(LED_Zals, LOW);
      Serial.println ("Abi LED");
    }
  }
}