1 Color Design
These are examples of a one color print on a garment at one location, for example the front of a shirt. To print a one color print on the back of the shirt would cost more. It would then be called "a one color print on each side". Yes, it costs to print black, it is not free. To change the print color on some of the shirts adds at least $20 each change.
When ordering shirts with one print color at one print location, expect to pay at least.