Learn how to create this graph here.
For a contour plot, Z values can be divided into many levels. These levels can be classified as major or minor.
In this graph, the Rainbow palette has been applied. The various colors represent different levels. (Only major levels are shown here; minor levels are hidden.)
The Colormap/Contours tab provides controls for customizing the levels, fill color, contour lines and contour labels. Click a column header to open a matching dialog.