def unique_color(n=1):
    """

    Returns one of 14 unique colors.  
    see https://xkcd.com/color/rgb/
    and https://matplotlib.org/tutorials/colors/colors.html
    
    Parameters
    ----------
    n : int, optional, default 1
        which unique color do you want [1..13]
        if n is not in 1..13, return mint
        
    Returns
    -------
    c : matplotlib.colors.Colormap
        one of 13 unique colors
        
 
    """
 
    if n == 1:
        c='xkcd:red'
    elif n== 2:
        c='xkcd:green'
    elif n== 3:
        c='xkcd:yellow'
    elif n== 4:
        c='xkcd:blue'
    elif n== 5:
        c='xkcd:orange'
    elif n== 6:
        c='xkcd:purple'
    elif n== 7:
        c='xkcd:cyan'
    elif n== 8:
        c='xkcd:magenta'
    elif n== 9:
        c='xkcd:lime green'
    elif n== 10:
        c='xkcd:candy pink'
    elif n== 11:
        c='xkcd:teal'
    elif n== 12:
        c='xkcd:lavender'
    elif n== 13:
        c='xkcd:brown'
    else:
        c='xkcd:mint'

    return c