int btn = 8;
int Rgb = 4;
int rGb = 3;
int rgB = 2;
int counter = 0;

bool buttonCheck = false;
bool btnState = LOW;
//bool 

void setup() {
  // put your setup code here, to run once:
  pinMode(btn, INPUT_PULLUP);
  pinMode(Rgb, OUTPUT);
  pinMode(rGb, OUTPUT);
  pinMode(rgB, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  btnState = !digitalRead(btn);

  Serial.println(counter);

  if(btnState == HIGH && buttonCheck == false){
    counter++;
    buttonCheck = true;
    delay(30);
  }else{
    delay(30);
    buttonCheck = false;
  }

  switch(counter){
      case 1:{
        digitalWrite(Rgb, HIGH);
        digitalWrite(rGb, LOW);
        digitalWrite(rgB, LOW);
        break;
      }
      case 2:{
        digitalWrite(Rgb, LOW);
        digitalWrite(rGb, HIGH);
        digitalWrite(rgB, LOW);
        break;
      }
      case 3:{
        digitalWrite(Rgb, LOW);
        digitalWrite(rGb, LOW);
        digitalWrite(rgB, HIGH);
        counter = 0;
        break;
      }
  }
}