I had tweaked my LockInfo headers before the update to 3.0 to make them clear. All I did was replace the overlay with a clear one.
BUT...with LockInfo 3.0 (and up) you can control this from right within the settings. If you go to Settings>LockInfo>Lockscreen>Appearance there are 3 sliders at the bottom that allow you to change the transparency of the headers, the section cells, and the background.
For instance, I've got my Section Headers slider all the way to the left (clear), but my Section Cells slider all the way to the right (completely opaque), and Background is all the way to the left (again, clear). That way, if I'm using a bright wallpaper, when I expand a section of LockInfo, I can more easily see the text.
Hope this helps!
I have my settings exactly like yours but it was still highlighted gray. It was driving me nuts until I found the setting to turn off the highlight for collapsed sections. Thanks.