When an automatic group row is created, its style object is determined automatically by using the GroupRowLevelStyles property. This property stores an array of style objects, and each item of the array is assigned to the corresponding level of grouping. For example, when the grid is being grouped by two columns, the first element of that array corresponds to the group rows created from the first column the grid is grouped by, and the second element - to the group rows created from the second column.

If the length of the array is less than the number of grouped columns, then the style object of a group row from nested levels which do not have the corresponding element in the GroupRowLevelStyles array will refer the style from the last element of the array. By default the GroupRowLevelStyles array has one item and all the group rows from any level refer this style object. This allows you to change the view of all the group rows you have simply by changing properties of this style object (you can do it even after you have grouped the grid because the Style property of each group row stores the reference to a style object from the GroupRowLevelStyles array).

iGrid1.GroupRowLevelStyles = new iGCellStyle[2];
iGrid1.GroupRowLevelStyles[0] = new iGCellStyle();
iGrid1.GroupRowLevelStyles[0].BackColor = Color.AliceBlue;
iGrid1.GroupRowLevelStyles[1] = new iGCellStyle();
iGrid1.GroupRowLevelStyles[1].BackColor = Color.SandyBrown;