When saving label and reloading, we do not update GUI

[EdwardMoyse]

Whilst looking into #633 I spotted something related: the label texts do not appear again in the GUI after a load
i.e. add four labels to the default MuonCombinedTracks collection, save, refresh phoenix then reload. The labels appear in 3D, but not in the GUI:

(This is part of usual issue with GUI and 3D not being synced, but this seems like it should be fixable)

[EdwardMoyse]

Also, the label colours were not updating when loading a state file.