Values are stored in the database upon selection by a user. Changing the value will result in a mismatch. We do not automatically update values when you change them. So for example if you change the value the user needs to edit their profile and select the value again. The only workaround for this is to manually update _comprofiler for that field to the new values. We'll provide a means of migrating field values in CB 3.x.

Normally values should be pretty generic with you only needing to change the label. Labels are entirely cosmetic and user facing. So for example you'd have a value of "opt_01" and a label of "Red".

Yes, instead of changing value you can just change the label. The label is what your users will see. Value is typically exclusively for storage, but will be used as label if you don't supply a label.