The answer to this is no, not at all. As with all the other techniques in this book, the techniques here are just options. If you create an alien species (for example), and they don't have a colorful Diamond, however, that group will most likely be pretty boring.
A friend once asked me, "So, if you have a group of friends, then that group too should have a Diamond, right?"
I replied that you only give a group a Diamond when you want that group to have its own distinct identity.