Matplotlib animation.ArtistAnimation.save is losing cmap colors as I increase the dpi

Question

I am currently trying to save a series of np arrays as a gif using the matplotlib animation.ArtistAnimation.save.

    cMap = colors.ListedColormap([black, cyan, magenta, yellow, blue, green, red])


    gal = []
    gallery = []
    fig = plt.figure()

    ax = plt.Axes(fig, [0., 0., 1., 1.])
    ax.set_axis_off()
    ax.set_aspect('auto')
    fig.add_axes(ax)


    for a in album:

        gal.append([plt.imshow(a, animated=True, cmap=cMap)])

    for g in gal:
        gallery.append(g)

    # for g in reversed(gal):
    #     gallery.append(g)

    ani = animation.ArtistAnimation(fig, gallery, interval=150, blit=True,
                                    repeat_delay=0)
    ani.save('cell translation/fire-and-ice.gif', dpi=500)
    plt.show()

The album contains a series of arrays that are used as the frames in the animation. The np arrays have seven different possible colors their values could correspond to. However, when I run the code as is the saved gif only has two colors (black and red) and the plt.show has maybe three. The number of colors in the animation increases as I decrease the dpi, but I'm not sure why.

Is this the best way to achieve the type of animation I'm looking for, and is there a way to keep all the colors as I increase the dpi? Also, is this enough context to explain what is happening?

Thank you for taking the time to try and help, learn, and understand.

single frame from the plt.show

full animation saved with current params

full animation with a dpi of 200

For context, each frame is a cellular automata path between the numerical values of the poem fire and ice by Robert Frost. Each line in the poem is 16 pixels tall and centered.