function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}


function agendaInkleuren () {
	var agenda = document.getElementById("agenda");
	var blokjes = agenda.getElementsByTagName("li");
	blokjes[1].style.backgroundColor = "#19738F";
	blokjes[2].style.backgroundColor = "#33839C";
	blokjes[3].style.backgroundColor = "#4D93A8";
	blokjes[4].style.backgroundColor = "#66A2B5";
}

addLoadEvent(agendaInkleuren);