A dilemma I know all to well 🙁 When I was working at a stuffy law firm for a few years I felt totally stifled when having to share an elevator with the “hip” people from the advertising firm in the building, they always looked so fun and relaxed. If you’re able to get a few staple pieces, a light colored blazer or pants with a fun (but appropriate) pattern on them would be great additions to your wardrobe. You can pair a blazer or cardigan with a cute dress to make it work appropriate. I also showed my own unique sense of style with makeup – a fun pop of color your lips while not too over the top can definitely kick up any look.
If those are a no go then you can also experiment with your hair. Up-dos, half pony tails or braids can look well put together and professional while showing your personality. Hope that helps!