I placed custom buttons on my form by using a for loop with code like this:

    // pass control array to each button
    this.myButton = new CustomButton.MyButton(this.Controls);
    this.Controls.Add(this.myButton);
    this.myButton.Location = new System.Drawing.Point(t,s);
    this.myButton.Size = new System.Drawing.Size(50,50);
    this.myButton.Text = "";
                       
But how can I reference each individual button during the click operation?

Answer: I wrote code to handle the Click event in the CustomButton.cs class, since this code is essentially the same for every button. When the player clicks a button, one of the 25 button objects gets its Click handler called.  That button can tell which one it is by it's index in the form's control array.  (By the way, I had to pass a reference to the form's control array to every button object in its constructor.  The button constructor just stashes the reference in a local variable for use later during clicks).   The form control array is:     System.Windows.Forms.Control.ControlCollection Then I could have code like this in the button click handler:                    if (myControlReference!=null)                    {                          myIndex = myControlReference.IndexOf(this);                          // now I know who I am and can also calculate                          // the index of neighboring buttons whose color                          // I must change; and I used their index to do it                     } For example, I can reach the preceding button object (assuming this is not the very first of the buttons) with syntax like                myControlReference[myIndex-1]; I also push myIndex onto a stack (which has to be accessible in a "global" class rather than from within one button object).  When the user wants to undo a move, I pop the top index from the stack and use it with the above syntax to tell the button to execute it's Click event (call the Click handler explicitly).  I also needed a method in my button class to toggle the color.  Neighbors call this to change the color of just that button.