Decker's UI is primarily black-and-white, but it actually uses a customizable 16-color palette. On the community forum[0] there's some discussion about dithering and importing colored photos. Users have taken advantage of color to make some really gorgeous projects[1].

[0]: https://itch.io/t/2668739/16-color-dithered

[1]: https://crowmorbid.itch.io/desker-deckmonth