What has probably happened here is the following sequence of events:
- All colour options were initially available
- The item was configured with all colour options
- The "shadow" colour option was then disabled by the admin
- The item was gifted without re-configuring the item first
What this means is that internally, the "shadow" colour is actually still configured. It only gets reset to a blank value if you were to configure the item after the option was disabled in the item settings.
The reason why the inventory says "not set" is that the inventory checks for both the admin option
and the configured value - in other words, if the admin option is turned off, it'll say "not set" even if internally the configured value still exists.
This issue affected all 4 style items (User Title Style, User Name Style, Thread Title Style and Post Style) and will be fixed in the next build.