זוהר שמות — דף קלט ע”א

Parasha Teruma — Folio 139a: The Zohar explains copper as a color combining elements of gold and silver, with the copper altar representing the small luminary governing the night. The blue-violet color of ritual fringes corresponds to the Throne of capital judgment, and its appearance in a dream signals spiritual danger. The change from blue to green marks the time for reciting the Shema. Purple gathers all colors into a single unity.