Well if you are not following MVVM, Add an event like below
void dgrdDataGrid_LoadingRow(object sender, DataGridRowEventArgs e)
{
DataGridRow row = e.Row;
var c = row.DataContext as YourDataGridOjbect;
if (c != null && c.IsSubscribed == true)
e.Row.Foreground = new SolidColorBrush(Colors.Yellow);
else
e.Row.Foreground = new SolidColorBrush(Colors.Red);
}