I can apply( in div element ) a background color and How ?

Answer 1

in test.css for example

div{
background: red;
color: white;
}

Answer 2

how about background-color ?

Answer 3

I think...

Answer 4

There are two ways to apply background color in div element.
div {
background:red;
color:dodgerblue;
} or
<div style="background-color:red;">Red background </div>