Here is an example of HTML code that can be used to change the background color of a webpage:
<!DOCTYPE html>
<html>
<head>
<style>
body {
background-color: #colorcode;
}
</style>
</head>
<body>
<h1>Hello World!</h1>
<p>This page has a colored background.</p>
</body>
</html>
The background color of the page is set in the <style> section, where the body element is selected and its background-color property is set to a specific color value.
You can change the color code to any color you want like for example #000000 for black, #FFFFFF for white and many more.
You can also use the name of the color instead of the color code.
<!DOCTYPE html>
<html>
<head>
<style>
body {
background-color: red;
}
</style>
</head>
<body>
<h1>Hello World!</h1>
<p>This page has a colored background.</p>
</body>
</html>
This will also change the background color to Red.