Is there a way to "mirror" materials on surfaces?

[EscapeArtist]

I'm looking to cut some editing time out of a project. The best way to describe what would like to do (and hope there is a plugin for) is to imagine a wall of boxes, the faces on one side are randomly colored. I need to match each texture on the opposite side of the wall, box for box, exactly with what is on the front. With several hundred boxes, you can see how this might be tedious. Is there any way to do this more quickly?

[Gaieus]

Select all the coloured faces, Ctrl+Move them onto the other side and while still selected, flip along the direction you've just moved them. They should merge with the faces on the other side (if there are any) overriding them. I often use similar techniques when texturing semicircular arches; you just position the texture on one facet and copy it along (around) the arch with radial array.

[EscapeArtist]

That's a great idea. Thanks!