\input zb-basic \input zb-ioport \iteman{io-port 06084814} \itemau{Keszegh, Bal\'azs} \itemti{Coloring half-planes and bottomless rectangles.} \itemso{Comput. Geom. 45, No. 9, 495-507 (2012).} \itemab Summary: We prove lower and upper bounds for the chromatic number of certain hypergraphs defined by geometric regions. This problem has close relations to conflict-free colorings. One of the most interesting type of regions to consider for this problem is that of the axis-parallel rectangles. We completely solve the problem for a special case of them, for bottomless rectangles. We also give an almost complete answer for half-planes and pose several open problems. Moreover, we give efficient coloring algorithms. \itemrv{~} \itemcc{} \itemut{proper hypergraph coloring; geometric hypergraph; conflict-free coloring; half-plane; axis-parallel rectangle} \itemli{doi:10.1016/j.comgeo.2011.09.004} \end