Setting background color for a datatable row in a plugin does not use the color variations

[vegegoku]

To reproduce add the following inline plugin to a datatable and make sure the table is not set to stripped 👍

tableConfig..addPlugin(new DataTablePlugin<Contact>() {
                    @Override
                    public void onRowAdded(DataTable<Contact> dataTable, TableRow<Contact> tableRow) {
                        int n = (tableRow.getIndex()%5);
                        if (n ==1) tableRow.addCss(dui_bg_yellow_l_1);
                        if (n ==2) tableRow.addCss(dui_bg_yellow_l_2);
                        if (n ==3) tableRow.addCss(dui_bg_yellow_d_3);
                        if (n ==4) tableRow.addCss(dui_bg_yellow_d_4);
                    }
                })

The rows are all using the main yellow color as background instead of the yellow color shades.

The rows should have different yellow shades background.