It's dye migration. It will almost always occur. You can try running your dryer low and slow and see if that helps.
It's not a navy or royal thing.
When the dye on the polyester fibers is heated it migrates into the plasticizers in your ink. Turn your dryer down (temp and speed) and see if that helps.
Or, use black ink.
We print them quite often. Turn the heat down and slow the dryer down. Test a couple and get it right.They want white ink.Do you think I should return the shirts and get 100 % cotton?