TTInventory uses DTG (direct to garment) printing, and this is applied to all apparel in the shop. Different fabrics will cause different affects in printing. For instance, the looser weave and combination of the polyester and cotton in the sweatshirts and hoodies cause a faded/vintage outcome with DTG printing. This is a pretty cool effect, but may not be ideal for you if you want a more opaque outcome.
Below is an example of print on a T-shirt with a black fabric that is 100% cotton, and to the right you will see the same print on the hoodies and sweatshirts which have a tri-blend fabric. You will notice the second image is a bit more faded. The darker the material is the more faded the print will be, which is why you will notice I do not provide darker color options for certain designs in TTInventory. You may notice the darker apparel very subtly peeking through the print, and this is normal and not a sign of a bad print.
If you have any more questions for me, please contact me at firstname.lastname@example.org !