You can edit the style of your quiz using the following classes:
.qpo_qpr_quiz class for entire quiz
.qpo_qpr_quiz {background-color: #ecf4f7;padding: 30px;}
.qpo_quiz_form class for form
.qpo_quiz_form {background-color: #fff;padding: 30px;}
.quiz_section class for this quiz’s page
.quiz_section {border: solid 1px #b9d6e2;}
.qpo_qpr_message_before class for message before text
.qpo_qpr_message_before {color: #0083ba;font-size: 14px;}
.qpo_qpr_question class for question text
.qpo_qpr_question {color: #333f4e;font-size: 18px;margin-bottom: 20px;}
.qpr_error class for error messages
.qpr_error {border: solid 1px #d95555;color: #d95555;font-size: 14px;padding: 20px;}
.qpo_qpr_question_comment class for comment fields
.qpo_qpr_question_comment {border: solid 1px #e4e6e9;font-size: 14px;padding: 20px;}
.qpo_qpr_comment_section_text class for message for comment section
.qpo_qpr_comment_section_text {font-size: 14px;color: #333f4e;}
.qpo_qpr_message_end class for message end text
.qpo_qpr_message_end {font-size: 14px;color: #333f4e;}
.qpo_qpr_quiz_link class for pagination buttons (Next/Previous)
.qpo_qpr_quiz_link {font-size: 14px;color: #009cde;border: solid 1px #009cde;padding: 5px;line-height: 100%;}
.qpo_qpr_timer class for the timer
.qpo_qpr_timer {color: #d33030;border: solid 1px #d33030;padding: 30px;line-height: 100%;font-style: italic;}
.qpo_horizontal_multiple class for horizontal multiple response answers
.qpo_horizontal_multiple {padding: 10px;line-height: 100%;}
.qpo_answer_open_text class for open answer question types
.qpo_answer_open_text {border: solid 1px #eee;line-height: 100%;padding: 15px;}
.qpo_answer_number class for number question types
.qpo_answer_number {border: solid 1px #eee;line-height: 100%;padding: 15px;}
.qpo_qpr_hint_link class for hint
.qpo_qpr_hint_link {border: solid 1px #ccebf8;padding: 15px;color: #0083ba;font-style: italic;}
.qpr_radio_answers class for multiple choice answers
.qpr_radio_answers {border: solid 1px #ccebf8;padding: 15px;}
.qpr_quiz_radio class for radio inputs
.qpr_quiz_radio {line-height: 120%;}
.qpo_horizontal_choice class for horizontal multiple choice answers
.qpo_horizontal_choice {line-height: 120%;}
.qpr_check_answers class for multiple response answers
.qpr_check_answers {color: #333f4e;font-size: 14px;line-height: 120%;}
.qpr_page_counter_message class for the pagination numbers
.qpr_page_counter_message {color: #0083ba;font-size: 14px;line-height: 100%;}
