Use the fill function to make shaded regions of any color tint. Here is an example.
1frompylabimport * 2 3x = arange(10) 4y = x 5 6# Plot junk and then a filled region 7plot(x, y) 8 9# Make a blue box that is somewhat see-through 10# and has a red border. 11# WARNING: alpha doesn't work in postscript output.... 12fill([3,4,4,3], [2,2,4,4], 'b', alpha=0.2, edgecolor='r')