Coloring Delaunay-edges and their generalizations

We consider geometric hypergraphs whose vertex set is a finite set of points (e.g., in the plane), and whose hyperedges are the intersections of this set with a family of geometric regions (e.g., axis-parallel rectangles). A typical coloring problem for such geometric hypergraphs asks, given an integer k, for the existence of an integer m=m(k), such that every set of points can be k-colored such that every hyperedge of size at least m contains points of different (or all k) colors. We generalize this notion by introducing coloring of t-subsets of points such that every hyperedge that contains enough points contains t-subsets of different (or all) colors. In particular, we consider all t-subsets and t-subsets that are themselves hyperedges. The latter, with t=2, is equivalent to coloring the edges of the so-called Delaunay-graph. In this paper we study colorings of Delaunay-edges with respect to halfplanes, pseudo-disks, axis-parallel and bottomless rectangles, and also discuss colorings of t-subsets of geometric and abstract hypergraphs, and connections between the standard coloring of vertices and coloring of t-subsets of vertices.