クリックで色が変わるJSコントロールボタンの実装方法

<button type="button" id="today" class="btn-link" onclick="todayDate()" style="color: #0062CC;">今日</button>

//昨日click
function yesterdayDate() {
  document.getElementById('title').value = getYesterdayDate(new Date());
  fetYesterdayData();
  today.css('color','#555555');
}
//今日click
function todayDate() {
  document.getElementById('title').value = formatterDateStr(new Date());
  fetTodayData();
  today.css('color','#0062cc');
}