require(vcd)
mosaic(matrix(1:6, 2, 3), gp=gpar(fill=c("red","gray","blue")), main="three
colors in each row")
mosaic(matrix(1:3, 1, 3), gp=gpar(fill=c("red","gray","blue")), main="only
one color in each row")


I anticipated three colors in the second plot.  My guess is that there is
a matrix subscript without drop=FALSE somewhere on the inside of one of the
functions.

This is with
Package: vcd
Version: 1.2-13
Date: 2012-02-19

on
version.string R Under development (unstable) (2013-02-02 r61822)
platform       i386-w64-mingw32
arch           i386
os             mingw32
system         i386, mingw32

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