Right click anywhere and choose Inspect Elements. Then switch to Console tab.

Inspect Elements allows you to see the HTML and styles on the page, and it can be used to make temporary edits to a webpage.
 In this case, you can use a backgroundColor property like this:

document.body.style.backgroundColor = "your color here";

Document is one of DOM objects and it represents the page.

Document object has main role in accessing HTML elements.
, Enjoy the color! Just remember that when you reload the page, it'll go back to white.
Open your browser console.

Insert JavaScript Code.

Press ↵ Enter from your keyboard to apply the changes.
,

You are done.
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