Aziraphale and Crowley wear white and black, respectively, which is a subtle nod to them being an angel and devil, respectively. This is also a subtle nod to Yin and Yang, from the Talmud, which fortells of Ragnarok, the anglicized version of Yom al Ayama, which—spoiler alert—is what the story is about.
Damnable Humbuggery 