<!DOCTYPE html>
<html>
<head>
<style>
 
fieldset{
width: 200px;
background-color:#F361A6;

}
</style>
</head>
<body>


 <form>
  <fieldset name="flower">
    <legend>flower</legend>

<input type="checkbox" name="flower" value="rose">rose<br>
<input type="checkbox" name="flower" value="ivy">ivy<br>
<input type="checkbox" name="flower" value="jasmin">jasmin<br>

  </fieldset>
</form> 


</body>
</html>