What type of personality do colleges want?

"Use the common application to show your personality". Great, what if I don't have one? Well of course I do but I'm just so similar to many other math and science kids that I won't stand out as a personality. I'm serious and I wrote a serious essay that is quite deep. It's not a bad essay but I feel like all it does is affirm my transcript, testing and extracurricular. I think that having a stand out personality would help at applying to Princeton or Carnegie to set me apart. But I don't know. It could backfire. What does everyone think, should I have my personal essay be serious or would it make sense to have a more unorthodox personality for the sciences. Thank you. And, if you want to read it then send me a personal message for the personal essay.