Reza Naserasr and Zhouningxin Wang (IRIF) will present the notion of circular coloring of signed graphs, as a common extension of the circular coloring of graphs and the 0-free coloring of signed graphs. In this work, they consider the problem of finding the best upper bound of the circular chromatic number of restricted families of signed graphs. In particular, they show that every signed bipartite planar graph of negative-girth 6 admits a circular 3-coloring.