 <p>How are you making the plot? <code>PlotDataItem</code> and <code>PlotCurveItem</code> classes both allow you to set the pen used when drawing. See:</p> <p><a href="http://www.pyqtgraph.org/documentation/graphicsItems/plotdataitem.html#pyqtgraph.PlotDataItem.setPen" rel="nofollow">http://www.pyqtgraph.org/documentation/graphicsItems/plotdataitem.html#pyqtgraph.PlotDataItem.setPen</a> <a href="http://qt-project.org/doc/qt-4.8/qpen.html" rel="nofollow">http://qt-project.org/doc/qt-4.8/qpen.html</a></p>