Several histograms on one set of axes?

Hi all,

maybe this is a daft question, but is there a simple way of drawing
several histograms on top of one another on the same axes?

Right now I can't even figure out how to change the bar colour in a
script. I've looked through the code in and this looks like it
*ought* to be right, but isn't:

ax1 = pylab.axes(...)
n, bins, patches = ax1.hist(data, color='r')

Any ideas would be very much appreciated ...