You don't need most of that code. A boolean already is true (1) or false (0). When you use int() on a boolean it will return this value. A boolean is false by default, so it's not needed to set the state. Also you don't need another variable to track the boolean's (0-1) state and you don't need a separate toggle method to change the state when all you want to do is toggle a boolean. Anyway, here's an example to show this in practice...

I've also added the code to change the captionLabel and the colors.

Code Example

1. import controlP5.*;
2. ControlP5 cp5;
3.  
4. boolean toggleValue;
5.  
6. void setup() {
7.   size(400,400);
8.   cp5 = new ControlP5(this);
9.   cp5.addToggle("toggleValue").setPosition(20,20).setSize(50,50)
10.      .setCaptionLabel("really?")
11.      .setColorBackground(color(255,0,0))
12.      .setColorForeground(color(0,0,255))
13.      .setColorActive(color(0,255,0));
14.   textAlign(CENTER, CENTER);
15.   textSize(300);
16. }
17.  
18. void draw() {
19.   background(0);
20.   text(int(toggleValue), width/2, height/2);
21. }