Dark shirts and light shirts print differently. Worth knowing before you order.
Light shirts (white, ash, light gray, light blue). One pass of ink on top of the fabric. Colors print true and vivid. Cheapest scenario per print. Hand is soft — the ink doesn't sit thick.
Dark shirts (black, navy, dark gray, charcoal, forest, burgundy). Need an underbase. The press lays down a layer of white ink, flashes it dry, then prints the colors on top. Two-pass minimum. Without the underbase, your red-on-black would print as a muddy maroon and your yellow-on-black would barely show.
What this means in practice. Dark-shirt prints cost slightly more (the underbase is an extra step). The hand is slightly stiffer because there's more total ink on the fabric. The print can feel a touch rubbery for the first wash before it relaxes.
Color tricks. Athletic-gold on black? Looks great. Bright orange on navy? Pops. Hot pink on charcoal? Loud and clean. The combination matters more than the absolute color choice.
What doesn't work as well. Photographic prints on dark shirts. Halftones and gradients on dark shirts (the underbase shows through). Very light yellow on black (hard to mix and match consistently).
What to do if you're unsure. Bring the artwork and the shirt color you want to the custom printing counter. We'll mock it up and tell you what to expect. Easier than guessing.