Use of inline CSS styling

I'm pretty good with CSS and it's best practices but there's always been one thing I was curious about.

Let's say you had 4 DIVs that all share the same class "section".

<div class="section">This is Section 1</div>
<div class="section">This is Section 2</div>
<div class="section">This is Section 3</div>
<div class="section">This is Section 4</div>

Here is the CSS for the sections

.section {
padding: 30px 0;
background-color: #fff;
}

The above code gives you 4 DIVs with 30px of padding on the top and bottom along with a white background.

Lets say you wanted the second DIV to have a black background but still have the same 30px padding. This is the ONLY DIV on this page (possibly the whole site) that will have a black background as a section.

Would this be an appropriate time to use the "style" attribute? Or would you give the DIV an ID or class and change it via your external CSS file?

I never understood what to do in these situations haha. Create a few more lines in my CSS for this ONE DIV or just use the style attribute and change it real quick?