@staticmethod
def add_color(bar):
    """add color as pango markup to a bar"""
    if bar in ['▁', '▂']:
        color = 'green'
    elif bar in ['▃', '▄']:
        color = 'yellow'
    elif bar in ['▅', '▆']:
        color = 'orange'
    elif bar in ['▇', '█']:
        color = 'red'
    colored_bar = "<span foreground='{}'>{}</span>".format(color, bar)
    return colored_bar
