This is highlighting questions with tags that are in your favorite tags. If you haven't manually added any favorite tags, the system will detect when you have a certain level of activity in a tag and infer one for you. If you manually add a favorite tag, the system will not infer a tag for you.

You can customize your favorite (and ignored tags) in your profile. You can also customize these settings in the right sidebar of the homepage and the /questions listing.

So, if you would prefer not to have any questions highlighted, you can simply add a nonsense "tag" to your favorites. Perhaps unicorn? (:

This is highlighting questions with tags that are in your favorite tags. If you haven't manually added any favorite tags, the system will detect when you have a certain level of activity in a tag and infer one for you. If you manually add a favorite tag, the system will not infer a tag for you.

You can customize your favorite (and ignored tags) in your profile. You can also customize these settings in the right sidebar of the homepage and the /questions listing.

So, if you would prefer not to have any questions highlighted, you can simply add a nonsense "tag" to your favorites. Perhaps unicorn? (: