this.button1.BackColor = Color.FromArgb(210, 80, 50);

LinearGradientBrush lgb = new LinearGradientBrush(r, Color.Black, Color.White, LinearGradientMode.Vertical);

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private Point rTopLeft = new Point(10, 10);
        private Size rSize = new Size(100, 100);

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            Graphics dc = e.Graphics;
            Rectangle r = new Rectangle(rTopLeft.X, rTopLeft.Y, rSize.Width, rSize.Height);
            LinearGradientBrush lgb = new LinearGradientBrush(r, Color.Black, Color.White, LinearGradientMode.Vertical);
            dc.FillRectangle(lgb, rTopLeft.X, rTopLeft.Y, rSize.Width, rSize.Height);
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if ((e.X >= rTopLeft.X && e.X <= rSize.Width + rTopLeft.X) && (e.Y >= rTopLeft.Y && e.Y <= rSize.Height + rTopLeft.Y))
                this.Text = "X: [" + e.X.ToString() + "], Y: [" + e.Y.ToString() + "]";
            else
                this.Text = "";         
        }
    }
}