a = np.arange(0,100,1).reshape(10,10)

cmap = plt.cm.jet
cmap.set_under('silver')
cmap.set_over('dimgray')

plt.imshow(a, cmap=cmap, interpolation='nearest',
           vmin=10, vmax=90)
plt.colorbar(aspect=40, pad=0.08, shrink=0.6,
             orientation='horizontal', extend='both')
plt.show()