At runtime you can test a column's AssignedValues property to determine whether a column property has been explicitly assigned. Values that are not explicitly defined are dynamically based on the associated field or the grid's defaults. 

You can undo property changes made to one or more columns. In the Columns editor, select the column or columns to restore, and then select Restore Defaults from the context menu. Restore defaults discards assigned property settings and restores a column's properties to those derived from its underlying field component 

At runtime, you can reset all default properties for a single column by calling the column's RestoreDefaults method. You can also reset default properties for all columns in a grid by calling the column list's RestoreDefaults method:

DBGrid1.Columns.RestoreDefaults;

DBGrid1->Columns->RestoreDefaults();