I want to change color of a specific area when clicked on a button. But get change the whole background instead only h2 index 0.

btn = document.createElement("button");
btn.innerHTML =  "L1";
btn.onclick = (changeColor) => {
    changeTags = document.getElementsByTagName("h2");
    c = changeTags[0];
    console.log(c);
    alert("This button is designated to Level 1 CM Approver Teams");
    document.body.style.backgroundColor = "red";
}