Free: 4 Color Printing Press Plans
freescreen_printing_press.jpg has free plans [PDF’s] for making your own 4-Color press. The key to multi color printing is accuracy and repeatability. Make sure if you attempt to build this that you build it very sturdy as mentioned on the website.

This four color, one station printing press was designed and built by Michael Phipps and Dan Mitchell. It is sturdy and very precise and can be built for less than $125, which is quite a bit less than even the cheapest commercial presses.

Get you own Free: 4 Color Printing Press Plans

Learn to Screen-Print Your Own T-Shirts – Make: Video Podcast