Более простой способ запрограммировать изменение фона по клику — HTML/CSS

// first we get all the buttons and text areas
var btns = document.querySelectorAll('.btn');
var mores = document.querySelectorAll('.more');

// we add an event listener by looping trough all the buttons
for (const btn of btns) {
  btn.addEventListener('click', handleClick);
}

// handle the button click
function handleClick(event){
  event.preventDefault();
  
  // remove the active class on ALL the buttons
  for (const btn of btns) {
    btn.classList.remove('active');
  }
  // add the active class on the clicked button
  event.target.classList.add('active');
  
  //remove the active class on all the text areas
  for (const more of mores) {
    more.classList.remove('active');
  }
  // here we get the data-show attribute of the clicked element 
  // and use it to show the right text area
  document.querySelector(`#${event.target.dataset.show}`).classList.add('active'); 
}

div.scrollmenu {
  background-color: #006668;
  overflow: auto;
  white-space: nowrap;
}

.btn.active{
  background: #000000;
}

.more{
  display: none;
}

.more.active{
  display: block;
}

<div class = "scrollmenu">
  <a class = "btn" href = "#" data-show = "more1" >Event 1</a>
  <a class = "btn" href = "#" data-show = "more2">Event 2</a>
</div>
<span id = "more1" class = "more">Display Event Here 1.</span>
<span id = "more2" class = "more">Display Event Here 2.</span>

.px-0 {
      padding-left: 0 !important;
      padding-right: 0 !important;
    }
    ul.nav.nav-tabs {
    	background-color: #006668;
    }
    ul.nav.nav-tabs li a,ul.nav.nav-tabs li a:hover {
    	color: #fff;
        border: 0;
        background-color: transparent;
    }
    ul.nav.nav-tabs li.active a,ul.nav.nav-tabs li.active a:hover {
    	background-color: #000;   
        border: 0;
        border-radius: 0;
        color: #fff;
    }
    .tab-content {
    	padding: 20px;
    }

<link rel = "stylesheet" href = "https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/css/bootstrap.min.css">
  <script src = "https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  <script src = "https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/js/bootstrap.min.js"></script>
<div class = "container-fluid px-0">
  

  <ul class = "nav nav-tabs">
    <li class = "active"><a data-toggle = "tab" href = "#home">Event 1</a></li>
    <li><a data-toggle = "tab" href = "#menu1">Event 2</a></li>
    <li><a data-toggle = "tab" href = "#menu2">Event 3</a></li>
    <li><a data-toggle = "tab" href = "#menu3">Event 4</a></li>
  </ul>

  <div class = "tab-content">
    <div id = "home" class = "tab-pane fade in active">
      <p>Display Event Here 1.</p>
    </div>
    <div id = "menu1" class = "tab-pane fade">
      <p>Display Event Here 2.</p>
    </div>
    <div id = "menu2" class = "tab-pane fade">
      <p>Display Event Here 3.</p>
    </div>
    <div id = "menu3" class = "tab-pane fade">
      <p>Display Event Here 4.</p>
    </div>
  </div>
</div>

const myBtns = document.querySelectorAll(".myBtn");
const descriptions = document.querySelectorAll(".description");

function myFunction(e) {
	myBtns.forEach( btn => {		
		btn.classList.remove("active");
	});
	
	descriptions.forEach( description => {
		description.classList.remove("show");	   
	});
	e.target.classList.add("active");
	document.querySelector("."+e.target.getAttribute("data-show")).classList.add("show");
}

div.scrollmenu {
  background-color: orange;
}
.hide {
	display: none;
}

.show {
	display: block;
}

.active {
	background-color: green;
}

<div class = "scrollmenu">
	<a onclick = "myFunction(event)" class = "myBtn" href = "#Event1" data-show = "more">Event 1</a>
	<a onclick = "myFunction(event)" class = "myBtn" href = "#Event2" data-show = "more2">Event 2</a>
</div>
	<span class = "hide description more">Display Event Here 1.</span>
	<span class = "hide description more2">Display Event Here 2.</span>

function myFunction(event) {
  var href = event.target.href.substring(event.target.href.indexOf('#') + 1);
  var id = event.target.id;
  var x = document.getElementsByTagName("span");
  var y = document.getElementsByTagName("a");
  var i,j;
  for (i = 0; i < x.length; i++) {
    x[i].style.display = 'none';
  }
  for (j = 0; j < y.length; j++) {
    y[j].style.backgroundColor = "#006668";
  }
  document.getElementById(href).style.display = 'inline';
  document.getElementById(id).style.backgroundColor = "#000000";
}

div.scrollmenu {
  background-color: #006668;
  overflow: auto;
  white-space: nowrap;
}
span {display: none;}

<div class = "scrollmenu">
  <a onclick = "myFunction(event)" id = "myBtn" href = "#Event1">Event 1</a>
  <a onclick = "myFunction(event)" id = "myBtn2" href = "#Event2">Event 2</a>
  <a onclick = "myFunction(event)" id = "myBtn3" href = "#Event3">Event 3</a>
  <a onclick = "myFunction(event)" id = "myBtn4" href = "#Event4">Event 4</a>
  <a onclick = "myFunction(event)" id = "myBtn5" href = "#Event5">Event 5</a>
  <a onclick = "myFunction(event)" id = "myBtn6" href = "#Event6">Event 6</a>
  <a onclick = "myFunction(event)" id = "myBtn7" href = "#Event7">Event 7</a>
  <a onclick = "myFunction(event)" id = "myBtn8" href = "#Event8">Event 8</a>
  <a onclick = "myFunction(event)" id = "myBtn9" href = "#Event9">Event 9</a>
  <a onclick = "myFunction(event)" id = "myBtn10" href = "#Event10">Event 10</a>
</div>
<span id = "Event1">Display Event Here 1.</span>
<span id = "Event2">Display Event Here 2.</span>
<span id = "Event3">Display Event Here 3.</span>
<span id = "Event4">Display Event Here 4.</span>
<span id = "Event5">Display Event Here 5.</span>
<span id = "Event6">Display Event Here 6.</span>
<span id = "Event7">Display Event Here 7.</span>
<span id = "Event8">Display Event Here 8.</span>
<span id = "Event9">Display Event Here 9.</span>
<span id = "Event10">Display Event Here 10.</span>