I only know the color of the turtle label can be changed. How about the size, position and font(such as if i wanna BOLD it). Thank you
I don't know about position and font. But you can change the size with right-click on the world (where the turtles live) and change the font size there. Here are some pages that deal with label changes: change label color and another that deals with labels of patches and a model in which the position of the labels is changed.