I have some sympathy for the Risograph people. Their process isn’t like ours: using movable types, but they operate with the same limitations — a single colour each pass and a limited means of reproduction.
This guide from the Hato Press explains the limitations — and the qualities of Riso printing — beautifully.
I also stumbled on this colour chart from Fredk. Aldous of Manchester –
Header image: Risograph flickr photo by Yannic Meyer shared under a Creative Commons (BY-NC) license