I use Createx for airbrushing but they also have a Acrylic Colors line (used for t shirts and screen printing) that has some sick colors (Pearl Gold) along with basic colors. Their Iridescent colors get dramatically lighter or darker depending on the angle you look at them from so there pretty sick.
with almost any paint that is intended for textiles and going in a washing machine you have to "heat-set" the paint. Once the paint is completely dry, iron on the backside of the fabric on high for about 5 mins. This effectively "glues" the paint into the shirt. Different companies recommend different methods so check with the company you end up using.
Good Luck With The Shirts