So, i was rewatching ep 33-34, and even after reading threads explaining cut scenes, i still feel a bit confused…
The change in dress could be due to the editing.
In Hengyang Sect, LSS is normally wearing white. It's like their uniform. But when she goes to the mortal realm (Jing capital), she is free to wear other colours.
HAHAAAA!!!!THIS CRACKED ME UP LOL.TRUTH OF THE CENTURY.Iqiyi loved the emotional damage youku gave us
Youku will go bankrupt not just from tissue costs and therapy sessions, but also because they need to reimburse our facial and beauty expenses after all the excessive ugly crying and sleepless nights.
K-Drama 
In Hengyang Sect, LSS is normally wearing white. It's like their uniform. But when she goes to the mortal realm (Jing capital), she is free to wear other colours.
Goodbye My Princess (GMP) is so good! If you survived TTEOTM, then watching GMP will be a piece of cake.
😭😭😭