Set link/cross reference color/underline in ResponsiveHTML5 output?

The generated output for a link looks like:

<span class="FM_URL"><a href="https://www.somewhere.com/">The Somewhere website</a></span>

The default css file has the following definition:

span.FM_URL {
font-family:"Arial Narrow";
font-style:normal;
font-weight:normal;
font-size:10.0pt;
color:#585858;
text-decoration:none;
letter-spacing:0.00em;
}

The output has the correct font (not the same as surrounding text,) but the color is blue and underlined.

When you say "paragraph tag to identify hyperlinks", do you mean in the css file or in FrameMaker?

As a test I added

/* A link that has not been visited */
a:link {
    color: #585858;
    text-decoration: none;
}
/* A link that has been visited */
a:visited {
    color: #585858;
    text-decoration: none;
}
/* A link that is hovered on */
a:hover {
    color: red;
    text-decoration: underline;
}
/* A link that is selected */
a:active {
    color: green;
    text-decoration: underline;
}

in my defualt css file (and imported again.) But it made no difference.

Which CSS? I haven't created or edited any CSS. (I expected FM to handle that.)

In the generated output there are five different css files, one with the name of my FM book, layout, layout.min, layoutfix.min and topic.min. But if I edit any of these, they will be replaced the next time I publish the html5 pages.

Where should I go to do changes that last?