Получить цвет фона от первого дочернего элемента div

let elements = document.getElementsByClassName("color-picker");
const background = elements[0].children[0].style.background;
console.info( background );

<div id = "my-color-picker-1" class = "color-picker jcolor-picker"> 
   <div data-type = "btn" style = "background: rgb(150,78,78)"></div>
</div>

let element = document.getElementsByClassName("color-picker")[0]
const bgColor = element.firstElementChild.style.background;
console.info( bgColor );

<div id = "my-color-picker-1" class = "color-picker jcolor-picker"> 
   <div data-type = "btn" style = "background: rgb(150,78,78)"></div>
</div>

let bgColor = document.querySelector("#my-color-picker-1").firstChild.nextSibling.style.backgroundColor

console.info(bgColor);

<div id = "my-color-picker-1" class = "color-picker jcolor-picker">
  <div data-type = "btn" style = "background: rgb(150,78,78)"></div>
</div>