Congratulations on qualifying for a complimentary premier membership!
The explanation is as given above and is a feature of the premier membership. If you wish to avoid the greying, then instead of clicking on the story names to go to them to bookmark them, use ctrl-click to open them in a new tab, do what you want with it, then close the new tab, which avoids reloading the page. Alternatively, use the site-based bookmark button to the left of the download buttons. If you are using a laptop, you can probably adjust the viewing angle to the point where the grey and the white look the same (I often seem to hit this by accident, which means archived authors are indistinguishable in the authors lists). Another option would be to refresh the page immediately it's loaded, so it's grey from the beginning.