Under Preferences, Content, click Colors and make sure that
"Allow pages to choose their own colors..." is checked.
If it is, then you may have a stuck setting in your profile.
Although visited link colour handling changed between 3.6 and 4,
visited links do correctly appear in the "visited" colour in the
Google search results on all our 17.0.1 systems.
As in your other support ticket, I would look at add-ons or a
bad profile as the most likely cause (try restarting the browser
with Option down to put it in Safe Mode, or reset your profile
using the link "How to reset your profile" at the bottom of this