Note: as of August, 2020, the Reporter of Decisions Style Sheet had not yet adopted the 21st edition of The Bluebook.
Washington Courts General Rule 14 requires that citations in court documents "conform with the format prescribed by the Reporter of Decisions." Generally, that means Bluebook format, but there are some exceptions (for instance, citing "RCW" instead of "Wash. Rev. Code"). Be sure to look at the Reporter of Decisions Style Sheet.