What us the tag used to add background color??

Answer 1

Background color was an attribute ("bgcolor") as Satnam mentioned, but has since been deprecated.

https://www.w3schools.com/tags/att_body_bgcolor.asp

Now, background color is a style property ("background-color"), also mentioned previously.

https://www.w3schools.com/cssref/pr_background-color.asp

However, tags represent elements, so technically speaking, there is no tag (element) specifically for background color.

Answer 2

with css prop "background-color"