* @return result  a LinkedHashSet of the colors found in sentences
     */
    private static LinkedHashSet<String> colors(
            ArrayList<ArrayList<String>> sentences) {
        LinkedHashSet<String> result = new LinkedHashSet<String>();
        for (int i = 0; i < sentences.size(); i += 1) {
            String type = sentences.get(i).get(1);
            if (type.equals(ASSERTION_TYPES.get(8))
                    || type.equals(QUESTION_TYPES.get(2))
                    || type.equals(QUESTION_TYPES.get(4))
                    || type.equals(QUESTION_TYPES.get(6))) {
                result.add(sentences.get(i).get(2));
            } else if (type.equals(ASSERTION_TYPES.get(0))
                    || type.equals(ASSERTION_TYPES.get(1))
                    || type.equals(ASSERTION_TYPES.get(2))
                    || type.equals(ASSERTION_TYPES.get(3))) {
                result.add(sentences.get(i).get(3));
            }
        }
        return result;
    }