change form color when minimized

I don't know how to make it change colors (don't think that's possible) however you can make it blink (you know like in a chatting program, when the window is minimized and you receive a message?). You need to call into the Windows API to do this. Here's some sample code that flashes every time the window loses focus and stops flashing when it receives focus again.

public partial class Form1 : Form
    {
        //Stop flashing. The system restores the window to its original state.
        public const UInt32 FLASHW_STOP = 0;
        //Flash the window caption.
        public const UInt32 FLASHW_CAPTION = 1;
        //Flash the taskbar button.
        public const UInt32 FLASHW_TRAY = 2;
        //Flash both the window caption and taskbar button.
        //This is equivalent to setting the FLASHW_CAPTION | FLASHW_TRAY flags.
        public const UInt32 FLASHW_ALL = 3;
        //Flash continuously, until the FLASHW_STOP flag is set.
        public const UInt32 FLASHW_TIMER = 4;
        //Flash continuously until the window comes to the foreground.
        public const UInt32 FLASHW_TIMERNOFG = 12;

        [StructLayout(LayoutKind.Sequential)]
        public struct FLASHWINFO
        {
            public UInt32 cbSize;
            public IntPtr hwnd;
            public UInt32 dwFlags;
            public UInt32 uCount;
            public UInt32 dwTimeout;
        }

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool FlashWindowEx(ref FLASHWINFO pwfi);

        public Form1()
        {
            InitializeComponent();
            this.Deactivate+=new EventHandler(Form1_Deactivate);
        }
      
        private void Form1_Deactivate(object sender, EventArgs e)
        {
            FlashWindowEx(this);
        }

        /// Minor adjust to the code above
        ///

        /// Flashes a window until the window comes to the foreground
        /// Receives the form that will flash
        ///

        /// The handle to the window to flash
        /// whether or not the window needed flashing
        public static bool FlashWindowEx(Form frm)
        {
            IntPtr hWnd = frm.Handle;
            FLASHWINFO fInfo = new FLASHWINFO();

            fInfo.cbSize = Convert.ToUInt32(Marshal.SizeOf(fInfo));
            fInfo.hwnd = hWnd;
            fInfo.dwFlags = FLASHW_ALL | FLASHW_TIMERNOFG;
            fInfo.uCount = UInt32.MaxValue;
            fInfo.dwTimeout = 0;

            return FlashWindowEx(ref fInfo);
        }
    }

Courtesy of PInvoke.net. LINK:

http://www.pinvoke.net/default.aspx/user32/FlashWindowEx.html