Crosshatching with multiple colors

[arronlacey]

Not an issue - more of a request - but I have to plot a geom_bar() plot where the colors of the bars represent the group they belong to. Some time, a bar will be within multiple groups. Is there a way to crosshatch the n number of colors into a particular bar to denote which groups it comes from? No fancy pattern - just a horizontal / vertical / diagnosis cross hatch that alternates between each group color.