Let Gbe a graph. A function  is called a proper outer sum coloring if  whenever u, vare adjacent where  The minimum span of foverall proper outer sum coloring fof Gis called outer sum chromatic number, denoted by  In this paper, we have obtained outer sum chromatic number of some standard graphs like path, cycle, wheel, complete graph, bipartite graph, etc. and compared  with the usual chromatic number

sum labeling, mod sum labeling, outer sum labeling, outer mod sum labeling.