Pilotage Law Article 25

When performing pilotage service, the pilot boat shall fly the signal as specified by International Code of Signal or ROC government authority, and the pilot signal light shall be exhibited during the nighttime.The signal flag or light shall be removed as soon as the pilot leaves the pilot boat or is out of service.
中文原文 引水法第25條
引水人執行領航業務時,其所乘之引水船,應懸掛國際通用或中華民國規定之引水船信號,夜間並應懸掛燈號。
引水人離去引水船或非執行業務時,應將引水船信號或燈號撤除。

English translation for reference only; the Chinese text prevails. Not legal advice.