Adding Hyperlink color

Tech challenged here. In the new Optimal theme, I need the hyperlinks within posts/pages/sidebars a different color (so people will know where to click). I know it’s now underline on hover, but I don’t see where to add a color.

Do I need to insert a line to the stylesheet under Typographical Elements somewhere in here:

}

a:hover {
text-decoration: underline;
}

Can you show how exactly so I don’t make an unfortunate rookie mistake? (I’m sure lots of other tech-challenged publishers will also want to know.)