how to change backgrounf color in html and css code example

Example 1: css change background color of page

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

Example 2: background color

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