Thank you so much for writing this!!
I don't understand chinese so such depth is lost on me. I even feel the urge to ask your opinions on similar things for other dramas that I like!
I'm very happy that the drama took the effort to make light colored clothes for Fang Fei, to visualise the lyrics as you described and to portray everything you mentioned. It adds a whole new layer to everything.
As for your question, here is my opinion:
- Shen Yu Rong has studied hard to reach his position, he is known to be impartial to political parties (ex in the exam between Li Jin and Ye Shi Jie he prefers Ye Shi Jie's answer) and is generally known to have the good of the people as his compass. He even lead his wife's funeral, even though she had supposedly cheated on him. So, in the public eyes he has a good reputation (white) almost until the end of the drama.
- Xiao Heng is known to be arrogant, he does what he likes, sometimes not even reporting to the Emperor about his actions, he tortures not only criminals but also suspects (who could be innocent), and if you catch his eye you're done for. It's no wonder then that everyone views him as a person that they want to avoid, even evil (black).
In the clothes scene Shen Yu Rong's cloak was white but it made her want to vomit, while Xiao Heng's clothes were black but she felt comfortable, warm and protected.
Considering everything I wrote above, my understanding is that not everything is as it seems.
What seems to be an excellent reputation and a hard working impartial scholar (white) is actually someone who killed his wife and was so cowardly that he refused to accept the implications of his actions up to the end, while the overbearing, arrogant noble (black) is actually a warm hearted person.
But this is not visible to outsiders who don't know about any of these things, hence the confusing colors of the clothes. Xue Fang Fei's clothes reflect her actual personality, but for Shen Yu Rong and Xiao Heng their clothes reflect how they're perceived by others.
Shen Yu Rong always wears light colored clothes, except for the red official's robe which also signifies the blood on his hands.
Xiao Heng always wears black, sometimes combined with red which signifies
- his vow to find out the truth behind his parents' death (his mom wore red when she fell off the cliff and he saw her)
- the blood on his hands (which is different from Shen Yu Rong's because Xiao Heng has killed criminals for the sake of the people)
- his thirst for life (in contrast to Shen Yu Rong's washed out white clothes and his pale appearance, resembling a dead man, Xiao Heng is a vibrant and active person).
Therefore, the seemingly clean and innocent white is a harbringer of death, while the deep abyss of black is a warm hearth for his wife and a pillar of strength for his people.