related to #847.
histstack should use fill_between instead of overlaying them on top of each other. (notice the green is mixed with blue instead of being pure green)
a = randn(1000)
b = randn(1000)
hist([a,b],histtype='stepfilled', stacked=True, alpha=0.5)
This should be fixed with the merging of #1724.
Seems to be fixed:
@ndawe: Thanks for confirming. I'm going to go ahead and close this bug then.