def score_style(polarity_value):
    """
    Returns colour of score progress bar based on polarity score.

    :param polarity_value: the polarity
    :return color: the colour of the progress bar
    """
    color = 'warning'
    if polarity_value < 33:
        color = 'danger'
    if polarity_value > 66:
        color = 'success'
    return color