Hyperlink Color and Underline settings?

Link colours are configurable in theme settings, under Color Settings.

In HTML, link elements do not exist without actually having a link assigned to them. They always link to something (even if that something is an invalid address). So they will always be coloured (as configured in theme settings).

Starting from this, there are several type of links:

• a and a:link – the standard normal link
• a:visited – a link that you’ve already clicked on and visited (at least once before in your browser)
• a:hover – a link you are currently hovering on
• a:active – a link at the instant you are clicking on

While the theme only colours two cases: the hover and all other cases combined, with custom CSS you can control them individually: http://www.w3schools.com/HTML/html_links.asp

To underline all links, this CSS does the trick:
a, a:hover { text-decoration: underline; }