This depends on the specific t-shirt design. There are some which come in 1-2 or two additional colors, and then there are others which accommodate a wider variety of options - more colors, more designs, size, placement and so forth.
For special orders with full customization, you can contact us directly and request a consultation with a one of our customer designer representatives. We are currently working on making a fully automated custom t-shirt maker, which will give you access to even greater creative solutions.