In a typical tri-blend tee, polyester brings strength and shape, cotton brings comfort and rayon brings softness and drape. The mix feels lighter and slinkier than cotton jersey, and because the three fibers take dye differently, most colors come out with a mottled, heathered tone.
Those same fibers change how it prints. Ink sits less evenly than on cotton, giving a soft, slightly faded look that many brands like. The polyester content means printers usually reach for low-cure or bleed-resistant inks to avoid dye migration and scorching. Discharge only partly works, since it cannot strip the polyester, and DTG color is less vivid than on 100% cotton.
Ask the printer which ink system suits your exact style and color, and check the maker's content label, since blend ratios vary between styles. See how to choose a blank for the wider trade-offs.