As woodenboat says, if you haven't set link properties in your css, the default for visited links is purple(ish). You can add link styles to your stylesheet (or to the head of your document):
a, a:link {
color: #000;
font-weight: normal;
text-decoration: none;
}
a:visited {
color: #000;
font-weight: normal;
text-decoration: none;
}
a:hover {
color: #666;
font-weight: bold;
text-decoration: underline;
}
These will show links and visited links black, and hovered-over links are grey, in bold and with an underline. White links would be #FFF.
If you have links in different divs that you want different colours for, you can specify the div before the link rules so that these links have different properties from other links on your page.
i.e. if your links are an a div called 'leftColumn', you can write rules for the links in just that div:
div#leftColumn a:link {
color: #000;
font-weight: normal;
}
div#leftColumn a:visited {
color: #000;
font-weight: normal;
}
div#leftColumna:hover {
color: #666;
font-weight: bold;
text-decoration: underline;
}