Change the order to determine plot lines are in front. Plotting area matters the most when you use area fills. The graphs below are the same, but with the plotting order reversed. Note that on the graph on the left the area fill from the one data set hides the other.
To change the plotting order of the data sets on a graph:
Click the Rotate/Flip button in the Change section of the Prism toolbar to reverse the front-to-back order of data sets on a graph.
To fine tune the front-to-back order, go to the Data Sets on Graph tab of the Format Graph dialog.