import numpy as np
import matplotlib.pyplot as plt

np.random.seed(42)
x = np.arange(10)
y0 = np.linspace(0, 1, 10)
y1 = np.linspace(0, 1, 10)
y2 = [0, 0, 0.25, 0, 0, 0, 0.25, 0, 0, 0]
y3 = np.linspace(0, 1, 10)


colors=['grey', 'blue', 'red', 'blue']

y = np.stack([y0, y1, y2, y3])
im = plt.stackplot(x, y, colors=colors, lw=0)

    # Color between x = 0 and the first array.
    color = ax._get_lines.get_next_color()
    coll = ax.fill_between(x, 0, stack[0, :],
                                      where=(stack[0, :] != 0), interpolate=True, edgecolor=color,
                                     facecolor=color, label=next(labels, None), **kwargs)
    coll.sticky_edges.y[:] = [0]
    r = [coll]

    # Color between array i-1 and array i
    for i in range(len(y) - 1):
        color = ax._get_lines.get_next_color()
        r.append(ax.fill_between(x, stack[i, :], stack[i+1, :],  
                                               where=(stack[i, :] != stack[i+1, :]), interpolate=True, edgecolor=color,
                                               facecolor=color, label=next(labels, None), **kwargs))