Change visited link color of notification list by using css doesn't work

I'm trying to change the color of item link in notification list after user clicked it. Here's my css code:

.ms-vb a:link {
  color: blue;
}

.ms-vb a:visited {
    color: red;
 }

The first part worked perfectly, all the links indeed changed to blue. But after I clicked the link, the color of link remained blue, which is supposed to changed to red.

So, what's the proper way to set up a css to change the color of visited link in notification list?