Are some of your colleagues your friends as well ? Or not ? I always find it very delicat to decide and draw a line there (not that it’s anything conscious).
Scientists generally spend a lot of times together because they work long hours, share regular drinks on friday evening, have days-out or extra-lab activities. So it’s inevitable that you get closer than “regular” colleagues. But that does not mean there is friendship there, right ? (Being Facebook friends does not count)
At the end, only time will tell you for sure. From experience, I can tell that I kept in touch with only a handful of people I met in labs. These are the ones you were and still are friends with.
PS: And this is what you call a lab party. Beer and wine on ice, in a box that normally contains dirty glassware. Isn’t that the nerdiest ?