White Dragon is Considered Neutral (Article ID 105)
Abstract: White Dragons (Soap), when represented as a zero, are considered neutral. When used as a zero, the soap isn’t considered a Dragon and isn’t required to match their partner suit. Therefore, in a grouping such as 2020, the 2s can be dots but do not have to be.
Question from a player: If I am playing a year hand where I need a White Dragon, must the number tiles be Dots?
Answer from the NMJL: “The White Dragon is usually a tile with a blue border around the edge. This is often referred to as “Soap.“ Only this Dragon can represent a zero. The Soap, when used as a zero, can be used with any suit. It can be used with Dots, Bams, Craks. There are four Soap Dragons. “
Source: Mah Jongg Made Easy 2020 page 6 para. 3
“White Dragon when used as a zero does not have to match the symbol tile it is used with. White Dragon as a zero is neutral”
Other answers from the NMJL: “The [number tile] may be played in Cracks, Bams, or Dots. A White Dragon, when used as a ZERO, is considered to be neutral and therefore can be used with any suit.”
Source for other answers:
National Mah Jongg League Bulletin Q&A (1983 page 4, 1984, 1991 page 12, 1992 page 5, 1993 page 13, 1995 page 5, 1997 page 6, 2014, 2015, 2018) https://www.nationalmahjonggleague.org