I am placing 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.TabIndex = 1;
    this.myButton.Text = "";
                       
But how do I reference each individual button during the click operation?

Answer: You write code in the CustomButton.cs class that is generalized for every button. When the player clicks a button, one of the 25 button objects gets its Click handler called; it 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 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, you 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).  You'll also want a method in your button class to toggle the color.  Neighbors call this to change the color of just that button.