Hey Andreas!
What I think you're looking for is an 'active link' color. This is a little bit outside my area of expertise, but I think what you would want to do is remove the visited link color (so all links appear black), and then set an active link color (so only the page you're on shows in blue).
This might be helpful:
https://stackoverflow.com/questions/2397370/change-link-color-of-the-current-page-with-css