Rakusu Talks

A rakusu (絡子) is a traditionally Japanese garment worn around the neck of Zen Buddhists who have taken the precepts. It can also signify Lay Ordination. It is made of 16 or more strips of cloth, sewn together into a brick-like pattern by the student during their period of preparation for their jukai or ordination ceremony.

There is no set standard, but the most common application of rakusu color is for the front of the rakusu to be black for priests and brown for teachers and sangha leaders. Occasionally in Western sanghas, the color green is used to signify that the wearer has been given Lay Entrustment, an authorization to teach at a basic level. The back of the rakusu is left white. The teacher will traditionally write the student's new Dharma name and occasionally their lineage.

From Rakusu on Wikipedia