slick carousel 'init' function doesn't work

all i use slick slider recently, but i need to add a script after slick carousel have been init.
I have try below code
DEMO codepan: https://codepen.io/kelvinspaces/pen/bGEXJaG
any idea to run the script after the slider have been load completly?

//Slick Slider    
$('.slider-container').slick({
      infinite: true,
      slidesToShow: 6,
      slidesToScroll: 6
    });
    

    $('.slider-container').on('init', function (event, slick) {
      alert('test');
      $('.test').css('background-color', 'red'); //RUN the script after slick slider have load completly.
    });

does anyone have any idea? or anyone can suggest a good performance and can fully customize carousel for me?