I may suggest NOT looping over each rows EACH time CellFormating is called, because it is called everytime A SINGLE ROW need to be refreshed.
Private Sub dgv_DisplayData_Vertical_CellFormatting(sender As Object, e As DataGridViewCellFormattingEventArgs) Handles dgv_DisplayData_Vertical.CellFormatting
Try
If dgv_DisplayData_Vertical.Rows(e.RowIndex).Cells("LevelID").Value.ToString() = "6" Then
e.CellStyle.BackColor = Color.DimGray
End If
If dgv_DisplayData_Vertical.Rows(e.RowIndex).Cells("LevelID").Value.ToString() = "5" Then
e.CellStyle.BackColor = Color.DarkSlateGray
End If
If dgv_DisplayData_Vertical.Rows(e.RowIndex).Cells("LevelID").Value.ToString() = "4" Then
e.CellStyle.BackColor = Color.SlateGray
End If
If dgv_DisplayData_Vertical.Rows(e.RowIndex).Cells("LevelID").Value.ToString() = "3" Then
e.CellStyle.BackColor = Color.LightGray
End If
If dgv_DisplayData_Vertical.Rows(e.RowIndex).Cells("LevelID").Value.ToString() = "0" Then
e.CellStyle.BackColor = Color.White
End If
Catch ex As Exception
End Try
End Sub