See my reply in your other thread.

For that matter, in Buddha's time, lay buddhists simply wear white to signify their purity in the precepts, and the Three Refuges are taken together with the Five Precepts. In a sense, how can one say that one is taking refuge in the Buddha, Dharma and Sangha, and yet act in contrary to the Dharma with respect to the training rules (Panca-sila, Five Precepts)?
Regarding the 海青, there are numerous origin stories, among which one story credits 梁武帝 for instituting the standardised 海青 for the monastics. This is similar to the upper garment with the "elephant ears" worn in the Tibetan tradition or the inner garment worn by the Theravadin tradition. Each locality adopted a flavor of its own in terms of their dress-code
and hopefully but maintained the core teachings of Four Noble Truth and Noble Eightfold Path that is common throughout all traditions.