To change the line width of body frame, you can make use of axes handle returned by ‘show’ function as mentioned by Cam. Also, adding customized markers at body frame can help in making joints more prominent. I have written the below code for the same:
config = homeConfiguration(puma1)
hlines(i).Color=[1 0 1];
You can customize the line properties as required by you. For more details on line properties, please refer this documentation link.
Hope this helps!