According to AS3000 you can still use yellow as one of the phases (only in NZ) until the next addition of the wiring rules comes out. You will then not be able to use either a yellow or green conductor excepting a green yellow for earth only as is the case for Australia at present.I am thinking they are allowing NZ to use up all the old yellow cable they have in stock.I have only seen yellow used as an active in old installs here. All is explained in AS/NZ 3000 2000 edition. section 3.8 I am assuming this is so you cant get an earth mixed up with an active as some earths have only 30% green tracing on yellow and when older can fade.
