On the Executive deck, in one of the Exec suites, you can find this unique laser rapier that when initially picked up, will take on the primary color of your chosen UI theme.
Unique Laser Rapier
On Executive deck, there is a rapier that assumes your UI color.
You can find this rapier here (south of the lounge area on the exec level):
This rapier will always be in this color, even if you change to another UI theme. Saving and reloading, then choosing a different UI theme will allow you to pick your favorite color of the seven available, excluding the default blue. This is the ONLY rapier in the game that uses this functionality, no others will do this.
As a result, the colors the laser rapier can be in are as follows, sorted by UI choice and excluding the default blue (as seen on the rapier in maintenance):
Comparing both rapiers
This video below will demonstrate all possible color choices for the unique laser rapier. Timestamps are in the description.