Heated blue hand is a special firing process on the hand, which is a kind of metal surface treatment process. When the steel parts are heated to 300 degrees Celsius (540 degrees Fahrenheit), the steel will be oxidized and the face color will be gradually becoming azure blue, then to the light blue after quenching. Here is the pciture for your reference on the heated blue hand on the dial.
From the watch industry, heated blue hand is attractive, wearable and high oxidation. It also shows that the watch is not low positioning, but also a symbol of status.