private void dataGridViewMaster_RowEnter(object sender, DataGridViewCellEventArgs e)
        {
            PaintRow(((DataGridView)sender).Rows[e.RowIndex], Color.Azure);
        }

        private void dataGridViewMaster_RowLeave(object sender, DataGridViewCellEventArgs e)
        {
           
            PaintRow(((DataGridView)sender).Rows[e.RowIndex], Color.Empty);
        }

//здесь заполняем DGV

 DataTable List = new DataTable();
 


                using (SqlConnection conn = new SqlConnection(connstr))
                {
                    conn.Open();
                    SqlCommand comm = conn.CreateCommand();
                    comm.CommandType = CommandType.StoredProcedure;
                    comm.CommandText = @"PListByUnit";
                    comm.Parameters.AddWithValue(@"unit", 26);

                    SqlDataAdapter da = new SqlDataAdapter(comm);
                    da.Fill(List);

                    dataGridViewAct.DataSource = List;
                 }

//PaintRow
private void PaintRow(DataGridViewRow victim, Color c)
        {
            foreach (DataGridViewCell DGVC in victim.Cells)
               DGVC.Style.BackColor = c;
                        

        }