SetConsoleAlpha

        static void SetConsoleAlpha(byte alpha)
        {
            IntPtr hwnd = GetConsoleWindow();
            SetWindowLong(hwnd, GWL_EXSTYLE, GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED);
            SetLayeredWindowAttributes(hwnd, 0, alpha, LWA_ALPHA);
        }

        [DllImport("kernel32.dll")]
        static extern IntPtr GetConsoleWindow();

        [DllImport("user32.dll")]
        static extern int SetWindowLong(IntPtr hwnd, int nIndex, long dwNewLong);

        [DllImport("user32.dll")]
        static extern int GetWindowLong(IntPtr hwnd, int nIndex);

        [DllImport("user32.dll")]
        static extern bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey, byte bAlpha, uint dwFlags);

        const int GWL_EXSTYLE = -20;
        const int WS_EX_LAYERED = 0x80000;
        const int LWA_ALPHA = 0x2;