All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no particular significance for the white or green colours in Islam. In fact, if there is any particular significance to any colour for Muslims, it is a conventional one not a legal one. So, the person who does not comply with this indications is not against the Shari‘a.
Allah knows best.