markers = (
    ("r", "+"),
    ("g", "o"),
    ("b", "*"),
    ("#bcd22", "+"),
    ("#17becf", "*"),
    ("g", "o"),
    ("b", "*"),
    ("#bcd22", "+"),
    ("#17becf", "*"),
    ("g", "o"),
    ("b", "*"),
    ("b", "*"),
)
c = [None] * 12
...
    z = model.labels_[i]
    c[z] = plt.scatter(pca_2d[i, 0], pca_2d[i, 1], c=markers[z][0], marker=markers[z][1])