scatter colormap example not exactly the same

scatter_cmap.py

from matplotlib.pyplot import scatter
import numpy as np
import matplotlib.pyplot as plt

x = [1, 2, 3, 4]
y = [4, 3, 2, 1]
alpha = [0.2, 0.3, 0.8, 1.0]
c = np.asarray([(0, 0, 1, a) for a in alpha])

plt.subplot(2, 1, 1)
s = scatter(x, y, color=c, edgecolors=c)


plt.subplot(2, 1, 2)
cdict4 = {'red':   ((0.0, 0.0, 0.0),
                    (1.0, 0.0, 0.0)),

          'green': ((0.0, 0.0, 0.0),
                    (1.0, 0.0, 0.0)),

          'blue':  ((0.0, 0.0, 0.0),
                    (1.0, 1.0, 0.0)),

          'alpha': ((0.0, 0.0, 0.0),
                    (1.0, 1.0, 0.0))
          }

plt.register_cmap(name='BlueAlpha', data=cdict4)

scatter(x, y, c=alpha, edgecolors=alpha, vmin=0, vmax=1)

plt.set_cmap('BlueAlpha')

plt.show()