How do I detect collisions between individual particles in LiquidFunProcessing?

Question

I'm using processing's liquidfun library to simulate particle interactions, such as changing color on collision, but I can't find a contactlistener for individual liquid particles. There's a built in contactlistener for JBox2D objects, but it doesn't apply to the particles themselves.

public void initscene() {

    ...
    
    world.setContactListener(new MyContactListener());

}

class MyContactListener implements ContactListener {

    @Override
    public void beginContact(Contact contact) {
        println(contact.getFixtureA());
        println(contact.getFixtureB());
    }
    
    @Override
    public void endContact(Contact contact) {
    }
    
    @Override
    public void preSolve(Contact contact, Manifold oldManifold) {
    }
    
    @Override
    public void postSolve(Contact contact, ContactImpulse impulse) {
      
    
      
    }

}

This only outputs anything when JBox2D objects come in contact, rather than all interactions, including between LiquidFun particles.