why are sites I have visited while private browsing still highlighted in search results?

When private browsing I would have thought that if you do a google search it shouldn't show sites you have visited before as highlighted (as visited recently) because in private browsing that info shouldn't be stored...however I find that this is indeed happening.

For instance if I have been to the New York Times website yesterday while in private browsing mode, and if today I google "New York Times", the link shows up as pink in the search results, indicating that I have already used this link before. But surely in private browsing this shouldn't be happening??