<div class="p-4 relative">
  <div class="my-bg absolute inset-0 bg-neutral-500">
  </div>
  
  <div class="relative flex gap-4">
    <div class="my-box w-24 h-24 bg-red-500"></div>
    <div class="my-box w-24 h-24 bg-sky-500"></div>
    <div class="my-box w-24 h-24 bg-lime-500"></div>
  </div>
  
</div>

const t = gsap.timeline();

t.from(".my-bg", {
  right: "100%"
}).from(".my-box", {
  opacity: 0,
  duration: 1,
  stagger: 0.5
}).to(".my-bg", {
  left: "100%"
});