  We study a graph coloring problem motivated by a fun Sudoku-style puzzle.
Given a bipartition of the edges of a graph into {\em near} and {\em far} sets
and an integer threshold $t$, a {\em threshold-coloring} of the graph is an
assignment of integers to the vertices so that endpoints of near edges differ
by $t$ or less, while endpoints of far edges differ by more than $t$. We study
threshold-coloring of tilings of the plane by regular polygons, known as
Archimedean lattices, and their duals, the Laves lattices. We prove that some
are threshold-colorable with constant number of colors for any edge labeling,
some require an unbounded number of colors for specific labelings, and some are
not threshold-colorable.
