Highlight the particular row in datagridview

bool validationPassed = true;
            string cellValue = string.Empty;
            try
            {
                for (int iRow = 0; iRow < ValidationGridView.Rows.Count; iRow++)
                {
                    for (int iCol = 0; iCol < ValidationGridView.Columns.Count; iCol++)
                    {
                        if (iCol == 5)  //because it is color column.It is set with default color
                            continue;

                        else if ((iCol == 1) || (iCol == 2))
                        {
                            string value = ValidationGridView[4, iRow].Value.ToString();   //checking the validation rules only for the User created queries.
                            if (value.ToUpper() == "TRUE")
                            {
                                cellValue = ValidationGridView.Rows[iRow].Cells[iCol].Value.ToString();
                                string colName = ValidationGridView.Rows[iRow].Cells[iCol].OwningColumn.Name.ToString();

                                if (string.IsNullOrEmpty(cellValue))
                                {
                                    if (colName == "Rule_Name")
                                    {
                                        System.Windows.Forms.DialogResult dialogResultForSameDescription = System.Windows.Forms.MessageBox.Show("Rule name cannot be empty.", "AVEVA P&ID", System.Windows.Forms.MessageBoxButtons.OK, MessageBoxIcon.Error);
                                    }
                                    else if (colName == "Description")
                                    {
                                        System.Windows.Forms.DialogResult dialogResultForSameDescription = System.Windows.Forms.MessageBox.Show("Description cannot be empty.", "AVEVA P&ID", System.Windows.Forms.MessageBoxButtons.OK, MessageBoxIcon.Error);
                                    }
                                    // ValidationGridView.Rows[iRow].Cells[iCol].Style.BackColor = Color.LightGreen;
                                     //ValidationGridView.CurrentCell = ValidationGridView.Rows[iRow-1].Cells[iCol-1];
                                    foreach (DataGridViewRow row in ValidationGridView.Rows)
                                    {
                                        if (row.Cells[0].Value.ToString() == "")
                                        {
                                            row.DefaultCellStyle.BackColor = Color.Tomato;
                                        }
                                    }
                                    validationPassed = false;
                                    break;
                                }
                                else
                                {
                                    if (colName == "Rule_Name")
                                    {
                                        bool chcksameRuleOrDescriptionExists = checkIfSameRuleNameOrDescriptionExist(iRow, 1, cellValue);
                                        if (chcksameRuleOrDescriptionExists)
                                        {
                                            System.Windows.Forms.DialogResult dialogResultForSameDescription = System.Windows.Forms.MessageBox.Show("Duplicate rule name exists.", "AVEVA P&ID", System.Windows.Forms.MessageBoxButtons.OK, MessageBoxIcon.Warning);
                                            // ValidationGridView.Rows[iRow].Cells[iCol].Style.BackColor = Color.LightGreen;
                                           // ValidationGridView.CurrentCell = ValidationGridView.Rows[iRow].Cells[iCol];
                                            validationPassed = false;
                                            break;
                                        }
                                        else
                                        {
                                            ValidationGridView.Rows[iRow].Cells[iCol].Style.BackColor = Color.White;
                                        }
                                    }
                                    else if (colName == "Description")
                                    {
                                        bool chcksameRuleExists = checkIfSameRuleNameOrDescriptionExist(iRow, 2, cellValue);
                                        if (chcksameRuleExists)
                                        {
                                            System.Windows.Forms.DialogResult dialogResultForSameDescription = System.Windows.Forms.MessageBox.Show("Duplicate description exists.", "AVEVA P&ID", System.Windows.Forms.MessageBoxButtons.OK, MessageBoxIcon.Warning);
                                            // ValidationGridView.Rows[iRow].Cells[iCol].Style.BackColor = Color.LightGreen;
                                             // ValidationGridView.CurrentCell = ValidationGridView.Rows[iRow].Cells[iCol];
                                            validationPassed = false;
                                            break;
                                        }
                                        else
                                        {
                                            ValidationGridView.Rows[iRow].Cells[iCol].Style.BackColor = Color.White;
                                        }
                                    }
                                }
                            }
                        }
                    }


                    if (validationPassed == false)
                        break;
                }
            }
            catch (System.Exception ex)
            {
            }
            return validationPassed;