Random Function Code

const int ButtonPin = 12;
const int LedGreen = 6;
const int LedYellow = 9;
const int LedRed = 11;
bool ReadValue =0;
bool LastReadValue =0;
int randomNum = 0;
bool Flag = 0;

void setup()
{
  pinMode (LedGreen, OUTPUT);
  pinMode (LedYellow, OUTPUT);
  pinMode (LedRed, OUTPUT);
  pinMode (ButtonPin, INPUT);
      Serial.begin(9600);
      randomSeed(analogRead(A0));
 digitalWrite (LedGreen, HIGH);
 digitalWrite (LedYellow, HIGH);
 digitalWrite (LedRed, HIGH);
 delay (20);

 digitalWrite (LedGreen, LOW);
 digitalWrite (LedYellow, LOW);
 digitalWrite (LedRed, LOW);
 delay (20);

pinMode (ButtonPin, INPUT) ;

Serial.begin (9600) ;
randomSeed (analogRead (A0)) ;

}
  boolean debounce(boolean last)
{
  boolean current = digitalRead(ButtonPin);
  if (last != current)
  {
    delay(5);
    current = digitalRead(ButtonPin);
  }
  return current;
}

void loop()
{
ReadValue= debounce(LastReadValue) ;
Serial.println(ReadValue);
if (LastReadValue == LOW && ReadValue == HIGH)
{
  randomNum=random(1, 7);
  if (randomNum == 1)
  {
    digitalWrite(LedGreen, HIGH);
    digitalWrite(LedYellow, LOW);
    digitalWrite(LedRed, LOW);
  }
}
else if (randomNum == 2)
{
    digitalWrite(LedGreen, LOW);
    digitalWrite(LedYellow, LOW);
    digitalWrite(LedRed, HIGH);
  }
  else if (randomNum == 3)
  {
    digitalWrite(LedGreen, LOW);
    digitalWrite(LedYellow, HIGH);
    digitalWrite(LedRed, HIGH);
  }
  else if (randomNum == 4)
{
  digitalWrite(LedGreen, HIGH);
    digitalWrite(LedYellow, HIGH);
    digitalWrite(LedRed, HIGH);
}
else if (randomNum == 5)
{
  digitalWrite(LedGreen, LOW);
    digitalWrite(LedYellow, HIGH);
    digitalWrite(LedRed, HIGH);
}
else if (randomNum ==6)
{
  digitalWrite(LedGreen, HIGH);
    digitalWrite(LedYellow, LOW);
    digitalWrite(LedRed, HIGH);
}
}