I like to use different colors for each part to make it easier to keep track of them. When I join two parts together and do various operations with them the two parts frequently become one part and take on one color. They also are identified as one part in structure tree. I can reverse the operation to get their identity back but I need to join the two parts together. How can I avoid each individual part losing their identity or how can I access the individual parts if they do lose their individual identity??