Hi Wolfgang,
your observation is correct: currently our wrapper around the SourceGrid.DataGrid formats all negative values in red when Method 'AddCurrencyColumn' is used.
Changing the background colour of a specific cell is difficult in a SourceGrid.DataGrid. I propose therefore that a positive value should be shown with red foreground text (like a negative value is currently) if a specific flag is set.
Please file a Bug for that. Include the information that the Method 'AddCurrencyColumn' in sgrdDataGrid.cs needs to be changed for that.