Fixed image change color

HTML

<div class="black"></div>
<div class="white"></div>
<div class="black"></div>
<div class="white"></div>
<div class="black"></div>
<div class="white"></div>
<div class="logo"></div>

CSS

.white{
  background-color:white;
  height: 400px;
}

.black{
  background-color:black;
  height: 400px;
}

.logo {
  width: 100px;
  height: 100px;
  width: 100px;
  height: 100px;
  background-color:white;
  position: fixed;
  top: 20px;
  left: 20px;
}