<div class="container">
  <div class="tall"></div>
</div>

body {
  margin: 0;
  padding: 0;
}

.container {
  background-image: linear-gradient(#f00, #0f0);
  background-size: 75% 100vh;
  background-repeat: no-repeat;
  background-attachment: fixed;
}

.tall {
  height: 300vh;
}