I don't think there ever have been color (urban) aerials for LA. If there were, they would have been stored on your hard drive, so they'd show up. What comes up now, white fuzz? Are you thinking of the LandSat tiles? If so, those are still there in the drop down.
All the tilesets show up in the drop down box regardless of whether they are enabled or not. But selecting them will go to either the next higher or next lower enabled tileset. If all are disabled you'll still get one of them (like AIR 1M) for example.