In order to change the fill color of the checkmark that is displayed in GridCheckBoxCellElement you should use the CellFormatting event:
private void RadGridView1_CellFormatting(object sender, CellFormattingEventArgs e)
var cell= e.CellElement as GridCheckBoxCellElement;
if (cell != null)
RadCheckBoxEditorElement editor = (cell.Editor as RadCheckBoxEditor).EditorElement as RadCheckBoxEditorElement;
RadCheckmark checkmark = editor.Children as RadCheckmark;
checkmark.Fill.BackColor = Color.White;
I hope this helps. Should you have any other questions do not hesitate to contact me.
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