how can I change toolstripmenuitem border color?

Question

I made a form like this (language c# - VisualStudio2012):
https://i.stack.imgur.com/5GEY1.jpg
How can I change the border color of toolstripmenuitem from white to another, or disable it ?
code:

class CustomProfessionalColors : ProfessionalColorTable
{
    public override Color MenuItemSelected
    { get { return Color.FromArgb(51, 51, 52); } }

    public override Color MenuBorder
    { get { return Color.Black; } }

    //fill màu item của menu khi mouse enter
    public override Color MenuItemSelectedGradientBegin
    { get { return Color.FromArgb(64, 64, 66); } }

    public override Color MenuItemSelectedGradientEnd
    { get { return Color.FromArgb(64, 64, 66); } }

    // chọn màu viền menu item khi mouse enter
    public override Color MenuItemBorder
    { get { return Color.FromArgb(51, 51, 52); } }

    // fill màu nút item của menu khi dc nhấn
    public override Color MenuItemPressedGradientBegin
    { get { return Color.FromArgb(27, 27, 28); } }

    public override Color MenuItemPressedGradientEnd
    { get { return Color.FromArgb(27, 27, 28); } }

    // fill màu thanh menu strip
    public override Color MenuStripGradientBegin
    { get { return Color.FromArgb(51, 51, 52); } }

    public override Color MenuStripGradientEnd       
    { get { return Color.FromArgb(51, 51, 52); } }
}

public Form1()
    {
        InitializeComponent();
        menuStrip1.Renderer = new ToolStripProfessionalRenderer(new CustomProfessionalColors());      
    }

Answer 1

This will do the job. It's actually not a border, but a background.

public override Color ToolStripDropDownBackground {
    get { return Color.Red; }
}