A RISO can typically print 150 pages per minute, so while the printing part of using a RISO is quite fast, the bulk of the work when creating a risograph is in the file preparation done in advance.
The RISO printer in the Knowledge Lab is a single drum printer and can only print one color at a time. The RISO does not recognize colors in a file, it only reads tonal value (black and white) so files have to be converted to grayscale for printing.
There are many different ways to prepare files for RISO printing but regardless of the technique used, the final file (or multiple files if printing more than one color) needs to meet the following requirements:
File preparation can be done in programs like Adobe Photoshop, InDesign, or Illustrator.
Purdue provides access to the Adobe Creative Suite on campus in Purdue IT supported computer labs, this map will show you where on campus you can access Adobe programs. The computers in the Knowledge Lab can also be used to access Adobe programs though most computer stations in the lab are connected to specific equipment so computer availability is limited to when that equipment is not in use.
For raster images that will be printed in a single color to make a monochromatic print, it is easiest to prep the file in Adobe Photoshop following these steps.
Risograph prints can be made with 2, 3, or 4 colors but each color layer needs to be saved as a separate grayscale pdf file. Below are tutorials for how to do color layer separations using Adobe Photoshop and Adobe Illustrator. Note: some video tutorials will have requirements or information that is specific for the studio that created the tutorial that are not applicable to the Knowledge Lab.
This is a great tutorial on how to create a two color print with full color and black & white images.
Full color photographs and other images can be created in RISO by doing CMYK channel separations using Photoshop. RISO inks do not directly translate to traditional Cyan, Magenta, Yellow, and Black (Key) ink so a RISO CMYK print will not be an exact reproduction of the original colors of an image but that's part of the fun and unique quality of RISO printing. For printing CMYK with the inks available in the Knowledge Lab, the usual choices are Cornflower Blue for Cyan, Fluorescent Pink for Magenta, Yellow, and Black which is used in the example below.

There are multiple ways to create separate files for different color layers, below are a couple of tutorial videos that demonstrate different techniques using Photoshop and Illustrator. Note: 2, 3, or 4 layer printing can be done with any combination of color ink of your choosing and does not require using the CMYK equivalent inks.
There are risograph studios around the world that can be great resources for tutorials and examples of the kinds of projects that a RISO printer makes possible. Below are also some other great resources that can help you take your risograph printing to the next level.