\pstGeonode[PosAngle={180,0}](1.5;24){A}(1.8;-31){B}
\pstGeonode{O}
\psset{arrows=->, arrowscale=2}
\pstArcOAB[linecolor=red, linewidth=1.5\pslinewidth]{O}{A}{B}
\pstArcOAB[linecolor=blue, linewidth=1.5\pslinewidth]{O}{B}{A}
\pstArcnOAB[linecolor=green]{O}{A}{B}
\pstArcnOAB[linecolor=magenta]{O}{B}{A}