This is actually standardized in CEA/CEDIA 2030a so there IS an industry standard to follow and it's recognized by CEA for use in CE devices.

"4.3.2 Speaker Wire and Connector Color Codes
All speaker cable conductors should be color coded, or distinctively marked to ensure proper polarity.
Two conductor cables generally contain a red and a black insulated conductor. The red conductor
shall be used for the positive terminals and the black conductor shall be used for the negative
terminals. Four conductor-unpaired cables generally contain red, black, white, and green conductors.
Red and black shall be positive and negative respectively, for the right speaker in each zone. White
shall be used for positive and green shall be used for negative to connect the left speaker. Other
colors may be used, but all connections must be consistent.
Speaker terminals shall be color coded in accordance with the color-coding scheme in CEA-863-A.
Special considerations should be taken for active speakers; follow manufacturer‘s instructions. "