How to get the colour of a pixel at X,Y using c#?

There's Bitmap.GetPixel for an image... is that what you're after? If not, could you say which x, y value you mean? On a control?

Note that if you do mean for an image, and you want to get lots of pixels, and you don't mind working with unsafe code, then Bitmap.LockBits will be a lot faster than lots of calls to GetPixel.

To get a pixel color from the Screen here's code from Pinvoke.net:

  using System;
  using System.Drawing;
  using System.Runtime.InteropServices;

  sealed class Win32
  {
      [DllImport("user32.dll")]
      static extern IntPtr GetDC(IntPtr hwnd);

      [DllImport("user32.dll")]
      static extern Int32 ReleaseDC(IntPtr hwnd, IntPtr hdc);

      [DllImport("gdi32.dll")]
      static extern uint GetPixel(IntPtr hdc, int nXPos, int nYPos);

      static public System.Drawing.Color GetPixelColor(int x, int y)
      {
       IntPtr hdc = GetDC(IntPtr.Zero);
       uint pixel = GetPixel(hdc, x, y);
       ReleaseDC(IntPtr.Zero, hdc);
       Color color = Color.FromArgb((int)(pixel & 0x000000FF),
                    (int)(pixel & 0x0000FF00) >> 8,
                    (int)(pixel & 0x00FF0000) >> 16);
       return color;
      }
   }