private Combination<Colors> generateTargetCombination() {
    List<Token<Colors>> targetTokens = new ArrayList<Token<Colors>>();
    targetTokens.add(new Token<Colors>(Colors.R));
    targetTokens.add(new Token<Colors>(Colors.O));
    targetTokens.add(new Token<Colors>(Colors.Y));
    targetTokens.add(new Token<Colors>(Colors.G));
    targetTokens.add(new Token<Colors>(Colors.B));  
    
    return new Combination<Colors>(targetTokens);
  }