After upgrading my color labels are only indicated with a white square on the thumbnails, not the original colors I've set. Also my edited renaming of the set of color labels. All my develop presets are kept.
Color labels are defined by the entry in the color label field. So if you edited the labels, and changed 'Red' into 'HDR' for example, that field now contains 'HDR'. Apparently the upgrade changed the label set to the default again, making 'HDR' an undefined color. You have to edit (or change to) the set with the same definitions.