When you make multiple range or column selections, then create a graph, Origin groups the resulting data plots in the graph layer. This applies to most 1D (statistical), 2D or a 3D XYY graphs (3D bar, 3D ribbon, 3D wall, and 3D waterfall plots).
Grouping provides for quick creation of presentation-ready graphs because each selection in the group is assigned a differentiating set of plot attributes (line color = black, red, green...; symbol shape = square, circle, triangle...; etc.). Assignments are made by cycling through a pre-determined (user-modifiable) palette of styles. For instance, the first selected range of cells in a set of grouped line plots might be denoted by a black line; the second selected range of cells might be denoted by a red line (the second color in the color list), the third selected range of cells by a green line (the third color in the color list), and so on.
For information on use of Layer Contents dialog box, see Managing Plots with the Layer Content Dialog Box in the Origin Help file.
For information on use of the Plot Setup dialog box, see Plotting with the Plot Setup Dialog Box in the Origin Help file.
The settings which Origin uses to differentiate grouped plots, are saved when you save the graph template (if you have a System Theme turned on, this can also affect the way in which grouped plots are differentiated; for more information, see System Themes).
To alter the way in which plot characteristics are assigned to grouped plots, first create your graph, then follow the procedures presented in Editing of Group Incremental Lists. For background information on customizing grouped plots, see Customizing Grouped Data Plots in the Origin Help file.
Note: The following data plot types cannot be grouped: Y error and XY error, vector graphs, and 3D XYZ scatter and trajectory graphs. Note also that label datasets associated with grouped Y datasets, cannot be grouped (label color does not automatically follow plot color). Conversely, you cannot ungroup the following data plot types: high-low-close charts, floating bar graphs, and floating column graphs.