Code:

DataTable dt2 = novo.eto();
            BindingSource bSource = new BindingSource();
            bSource.DataSource = novo.eto();
            dataGridView1.DataSource = bSource;


            var query = from order in dt2.AsEnumerable()
                        where order.Field<int?>("stanje") < 5 // nullable type 

                        select new
                        {
                            STANJE = order.Field<int>("stanje"),
                            ID = order.Field<int>("id"),
                            
                        };

            foreach (var proradivise in query)
            {
                 

                if (proradivise.STANJE < 5)
                {
                    this.dataGridView1.Rows[proradivise.ID - 1].DefaultCellStyle.BackColor = Color.Red;
//Umjesto proradivise.ID, treba mi trenutni DGV.IndexOf
                }
                else
                {
                    this.dataGridView1.Rows[proradivise.ID-1].DefaultCellStyle.BackColor = Color.Green;
                }
            }