how to change background color in css

body {
  background-color: green;
}

body {
  background-color: lightblue;
}
 

html,body {
  background-color: red;
}

body{
  background: lightblue;
}

/* Use the following code: */
html {background-color: #fefefe;} 
/* You can change the hexedecimal code to RGB, RGBA, name & more colors!*/

//javascript type css:
document.body.style.backgroundColor = "blue";
// or inline css:
<div style="background-color: blue;"></div>