colors = ['navy', 'slateblue', 'cornflowerblue', 'powderblue', 'ivory',
          'navajowhite', 'lightsalmon', 'coral', 'orangered', 'firebrick']
fig, ax = plt.subplots()
img = ax.contourf(v, np.linspace(1,3,11), colors=colors)
fig.colorbar(img, orientation='horizontal')