Polyester is colored with disperse dyes, which can sublimate (go from solid straight to gas) when heated. In the dryer, that dye can rise into a plastisol print, so a white logo on a red performance shirt slowly turns pink. Sometimes it shows at once; sometimes it appears days later as the dye keeps moving.
Printers fight it with low-bleed or bleed-blocker inks, gray or black blocker underbases that trap the dye, and the lowest cure temperature the ink allows. Low-cure plastisols exist largely for this reason. Reds, maroons and other deep colors are frequent offenders, as are sublimated jerseys and some heathers and tri-blends.
If your order uses polyester or blends, tell the printer the exact blank and color, and ask how they test for migration. A test print left to sit for a day or two is a sensible step on any untried combination. More in the inks guide.