"Uniforms" for certain occasions

When I used to fly for work, I used to always wear the same thing when I flew out. It didn't start out intentional, but it worked, so I kept doing it. Last year I went to the beach and wore a white dress with pink flamingos and black leggings. I think I'm going again in a few days and I'm planning to wear that again. Things went so well last time. Anyone else have an official uniform for certain things? What is it?