上から #3a5976 と下から #2c4762
読みづらくてすみません、テキストエディタにコピーしてください
<html>
  <head>
    <style>
      body {
        background-image: linear-gradient(bottom, rgb(70,125,149) 19%, 
                          rgb(98,163,179) 60%, 
                          rgb(56,122,122) 80%);
        background-image: -o-linear-gradient(bottom, rgb(70,125,149) 19%, 
                          rgb(98,163,179) 60%, 
                          rgb(56,122,122) 80%);
        background-image: -moz-linear-gradient(bottom, rgb(70,125,149) 19%, 
                          rgb(98,163,179) 60%, 
                          rgb(56,122,122) 80%);
        background-image: -webkit-linear-gradient(bottom, rgb(70,125,149) 19%, 
                          rgb(98,163,179) 60%, 
                          rgb(56,122,122) 80%);
        background-image: -ms-linear-gradient(bottom, rgb(70,125,149) 19%, 
                          rgb(98,163,179) 60%, 
                          rgb(56,122,122) 80%);
           }
    </style>
  </head>
  <body>
  </body>