How to change navbar color in UIkit?

Question

css

I came across a simple and very cool framework (for me) - UIKit.
I need to make the navbar blue, I copied the code from here - https://getuikit.com/docs/navbar
Next, I chose the appropriate navbar -
Here is the code:

spoiler

<nav class="uk-navbar-container" uk-navbar>

    <div class="uk-navbar-left">

        <ul class="uk-navbar-nav">
            <li class="uk-active"><a href="#">Active</a></li>
            <li>
                <a href="#">Parent</a>
                <div class="uk-navbar-dropdown">
                    <ul class="uk-nav uk-navbar-dropdown-nav">
                        <li class="uk-active"><a href="#">Active</a></li>
                        <li><a href="#">Item</a></li>
                        <li><a href="#">Item</a></li>
                    </ul>
                </div>
            </li>
            <li><a href="#">Item</a></li>
        </ul>

    </div>

    <div class="uk-navbar-right">

        <ul class="uk-navbar-nav">
            <li class="uk-active"><a href="#">Active</a></li>
            <li>
                <a href="#">Parent</a>
                <div class="uk-navbar-dropdown">
                    <ul class="uk-nav uk-navbar-dropdown-nav">
                        <li class="uk-active"><a href="#">Active</a></li>
                        <li><a href="#">Item</a></li>
                        <li><a href="#">Item</a></li>
                    </ul>
                </div>
            </li>
            <li><a href="#">Item</a></li>
        </ul>

    </div>

</nav>

But no matter how I try to change the color ( https://getuikit.com/docs/background), nothing comes out for me. Where to add this CSS class with color - .uk-background-primary(in the documentation, this color means blue)?
The color can be changed if specified style="background: #000;"in the <nav>, but I would very much like to do this using the framework and CSS styles.