Which CSS?

Both of those are CORE XENFORO CSS classes.

the title uses the core class

HTML:

a:link, a:visited

so you will have to over ride that with something like this...

HTML:

.showcaseListItem .main .title a:link,
.showcaseListItem .main .title a:visited
{
color: #176093;
}

The 2nd one is HTML output by the core xenforo date helper. You MIGHT be able to use the same trick above (replace a.link with .faint a

HTML:

body .faint, body a.faint, body .faint a {
    color: #c8c8c8;
}