I'll try to hold back my curious world-building brain (I wanna read the employee handbook! Who else works here? how'd they all find their way to this job?), and just answer the question.
Number 4 is the most interesting to me.. it looks like she'd rather be doing something else, or maybe isn't wild about this job? She looks a little resigned... (also is the only one not adhering to the dress code)
Great work, I love these characters!