ComboBoxColorSelector

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Text;
using System.Linq;
using System.Windows.Forms;

    [DesignerCategory("Code")]
    [ToolboxItem(true), ToolboxBitmap(typeof(ComboBox))] // Generic: replace with custom Icon
    public class ComboBoxColorSelector : ComboBox
    {
        private Color defaultColor = Color.Transparent;
        public ComboBoxColorSelector() => InitializeComponent();

        private void InitializeComponent()
        {
            DropDownStyle = ComboBoxStyle.DropDownList;
            DrawMode = DrawMode.OwnerDrawVariable;
            FlatStyle = FlatStyle.Flat;
            FormattingEnabled = false;
        }

        // Read this Property value when a selection is made
        // This is the Color currently selected
        public Color SelectedColor { get; private set; }

        protected override void OnHandleCreated(EventArgs e)
        {
            base.OnHandleCreated(e);
            if (DesignMode || Items.Count > 0) return;
            Color[] colors =
                Enum.GetValues(typeof(KnownColor)).OfType<KnownColor>()
                    .Select(kc => Color.FromKnownColor(kc)).ToArray();
            DisplayMember = "Name";
            DataSource = colors;
        }

        int previousFound = 0;
        protected override void OnKeyPress(KeyPressEventArgs e)
        {
            base.OnKeyPress(e);
            if (char.IsLetter(e.KeyChar)) {
                int found = FindString(e.KeyChar.ToString().ToUpper(), previousFound);
                if (found > -1) {
                    previousFound = found;
                    SelectedIndex = found;
                }
                else {
                    previousFound = 0;
                }
            }
        }

        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            e.DrawBackground();
            if (e.Index < 0) return;

            e.Graphics.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
            var itemColor = (Color)Items[e.Index];
            using (Brush itemBrush = new SolidBrush(itemColor))
            using (Brush textBrush = new SolidBrush(e.ForeColor)) {
                e.Graphics.FillRectangle(itemBrush, new Rectangle(new Point(e.Bounds.X + 1, e.Bounds.Y + 1), new Size(e.Bounds.Height - 1, e.Bounds.Height - 1)));
                e.Graphics.DrawString(itemColor.Name, e.Font, textBrush, new Point(e.Bounds.X + e.Bounds.Height + 10, e.Bounds.Y));
            }
            e.DrawFocusRectangle();
            base.OnDrawItem(e);
        }

        protected override void OnMeasureItem(MeasureItemEventArgs e)
        {
            e.ItemHeight = Font.Height + 4;
            base.OnMeasureItem(e);
        }

        protected override void OnSelectionChangeCommitted(EventArgs e)
        {
            if (SelectedIndex >= 0) SelectedColor = (Color)SelectedItem;
            base.OnSelectionChangeCommitted(e);
        }

        protected override void OnSelectedIndexChanged(EventArgs e)
        {
            if (SelectedIndex >= 0) SelectedColor = (Color)SelectedItem;
            base.OnSelectedIndexChanged(e);
        }

        protected override void OnParentForeColorChanged(EventArgs e)
        {
            base.OnParentForeColorChanged(e);
            if (this.Parent != null) defaultColor = this.Parent.ForeColor;
        }
    }