  We present transfer matrices for the zero-temperature partition function of
the $q$-state Potts antiferromagnet (equivalently, the chromatic polynomial) on
cyclic and M\"obius strips of the square, triangular, and honeycomb lattices of
width $L_y$ and arbitrarily great length $L_x$. We relate these results to our
earlier exact solutions for square-lattice strips with $L_y=3,4,5$,
triangular-lattice strips with $L_y=2,3,4$, and honeycomb-lattice strips with
$L_y=2,3$ and periodic or twisted periodic boundary conditions. We give a
general expression for the chromatic polynomial of a M\"obius strip of a
lattice $\Lambda$ and exact results for a subset of honeycomb-lattice transfer
matrices, both of which are valid for arbitrary strip width $L_y$. New results
are presented for the $L_y=5$ strip of the triangular lattice and the $L_y=4$
and $L_y=5$ strips of the honeycomb lattice. Using these results and taking the
infinite-length limit $L_x \to \infty$, we determine the continuous
accumulation locus of the zeros of the above partition function in the complex
$q$ plane, including the maximal real point of nonanalyticity of the degeneracy
per site, $W$ as a function of $q$.
