How do I programmically change the Foreground color in a ListBox

Try this code 

public void FillListBoxColoredText(ListBox LBx, List liststX)
{
    int iCount = liststX.Count();
    for (int ii = 0; ii < iCount; ii++)
    {
        if (liststX[ii].Contains("blue"))
            LBx.Items.Add(liststX[ii], System.Drawing.Color.Blue);
        else if (liststX[ii].Contains("red"))
            LBx.Items.Add(liststX[ii], System.Drawing.Color.Red);
        else if (liststX[ii].Contains("green"))
            LBx.Items.Add(liststX[ii], System.Drawing.Color.Green);
    }
}

To change the foreground color of items in a ListBox programmatically in C#, you can use the DrawItem event and customize the drawing of each item.

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

namespace ListBoxColorChange
{
    public partial class Form1 : Form
    {
        private ListBox listBox1;

        public Form1()
        {
            InitializeComponent();
            InitializeListBox();
        }

        private void InitializeListBox()
        {
            listBox1 = new ListBox();
            listBox1.Dock = DockStyle.Fill;
            listBox1.DrawMode = DrawMode.OwnerDrawFixed; // Set draw mode to custom
            listBox1.DrawItem += new DrawItemEventHandler(listBox1_DrawItem);
            Controls.Add(listBox1);

            List items = new List { "Red", "Green", "Blue" };
            foreach (string item in items)
            {
                listBox1.Items.Add(item);
            }
        }

        private void listBox1_DrawItem(object sender, DrawItemEventArgs e)
        {
            if (e.Index < 0) return;
            e.DrawBackground();

            string itemText = listBox1.Items[e.Index].ToString();

            // Set the text color based on the item text
            Color textColor = Color.Black;
            if (itemText.Contains("Red"))
                textColor = Color.Red;
            else if (itemText.Contains("Green"))
                textColor = Color.Green;
            else if (itemText.Contains("Blue"))
                textColor = Color.Blue;

            // Draw the item text with the determined color
            using (SolidBrush brush = new SolidBrush(textColor))
            {
                e.Graphics.DrawString(itemText, e.Font, brush, e.Bounds, StringFormat.GenericDefault);
            }

            e.DrawFocusRectangle();
        }
    }
}

the listBox1_DrawItem event handler is used to customize the drawing of each item in the ListBox. It checks the text of each item and sets the colour accordingly. You'll need to adjust the colour logic to suit your specific requirements.