By default <a> elements already use the right link color and apply an underline on hover. So in most cases the .Link class is not really needed.
Some text with a <a href="#url">link</a>Some text with a <a href="#url" class="Link">link</a>
If you like to override the default link styles you can do so with the following link utilities. Bear in mind that link styles are easier for more people to see and interact with when the changes in styles do not rely on color alone.
Use .Link--primary to turn the link color to blue only on hover.
<p class="color-fg-muted">Some text with a <a class="Link--primary" href="#url">Link--primary</a></p>
Use .Link--secondary for a more subtle link color that turns blue on hover.
Some text with a <a class="Link--secondary" href="#url">Link--secondary</a>
Use .Link--muted also removes the underline on hover. Tip: You can also use the .no-underline utility to do the same for .Link--primary.
<p>Some text with a <a class="Link--secondary no-underline" href="#url">Link--muted</a></p><p>Some text with a <a class="Link--primary no-underline" href="#url">Link--primary no-underline</a></p>
Use .Link--onHover to make any text color used with links to turn blue on hover. This is useful when you want only part of a link to turn blue on hover.
<a class="color-fg-muted no-underline" href="#url">A link with a partial <span class="Link--onHover">Link--onHover</span></a>
The .Link class can be nested inside an <a> element if only part of it should be styled like a link.
<a class="color-fg-default no-underline" href="#url">A nested <span class="Link">Link</span></a>
Link classes in combination with color utilities lets you colorize information separately inside of a link but have all of the link turn into one color on hover.
<a class="Link--primary text-bold" href="#url"><svg class="octicon octicon-flame color-fg-danger" viewBox="0 0 12 16" version="1.1" width="12" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M5.05.31c.81 2.17.41 3.38-.52 4.31C3.55 5.67 1.98 6.45.9 7.98c-1.45 2.05-1.7 6.53 3.53 7.7-2.2-1.16-2.67-4.52-.3-6.61-.61 2.03.53 3.33 1.94 2.86 1.39-.47 2.3.53 2.27 1.67-.02.78-.31 1.44-1.13 1.81 3.42-.59 4.78-3.42 4.78-5.56 0-2.84-2.53-3.22-1.25-5.61-1.52.13-2.03 1.13-1.89 2.75.09 1.08-1.02 1.8-1.86 1.33-.67-.41-.66-1.19-.06-1.78C8.18 5.31 8.68 2.45 5.05.32L5.03.3l.02.01z"></path></svg>Hot<span class="color-fg-muted">potato</span></a>