Ext modifies GridPanel data and font color, etc., not just EditGridPanel
First get the selected row (of course you can also get the cell):
var selectedRow = grid.getSelectionModel().getSelected();
Modify the settings:
selectedRow.set("key","value");
Modify the background color, first get the row number, and then get the view object of the row:
var selectedIdx = grid.store.indexOf(selectedRow);
var selectedView = grid.getView().getRow(selectedIdx);
Modify row css attributes:
selectedView.style.color="# FF0000"; //The font turns red