C# drawline with RGB spectrum

Hi, I've been thinking for a long time about how to create a project in C# in winforms, where I select 2 points with the mouse and create a line between them that will have the whole RGB spectrum.

public partial class Form1 : Form
    {
        class Line
        {
            public Point Start { get; set; }
            public Point End { get; set; }
        }

        public Form1()
        {
            var pb = new PictureBox { Parent = this, Dock = DockStyle.Fill };
            Line line = null;

            pb.MouseMove += (s, e) =>
            {
                if (e.Button == MouseButtons.Left)
                {
                    line.End = e.Location;
                    pb.Invalidate();
                }
            };
            pb.MouseDown += (s, e) =>
            {
                if (e.Button == MouseButtons.Left)
                    line = new Line { Start = e.Location, End = e.Location };
            };
            var lines = new List<Line>();
            pb.MouseUp += (s, e) =>
            {
                if (e.Button == MouseButtons.Left)
                    lines.Add(line);
            };
            pb.Paint += (s, e) =>
            {
                if (line != null)
                    e.Graphics.DrawLine(Pens.Red, line.Start, line.End);

                foreach (var l in lines)
                    e.Graphics.DrawLine(Pens.Silver, l.Start, l.End);
            };
        }
    }