Dreamworld did have custom uniforms for Nick Central when it was around, and Gold Rush Country (Eureka and Thunder River, Log Ride and sometimes Giant Drop) had a different uniform as well similar to Wild West Falls but in blue. I think Motocoaster also had a seperate polo shirt for at least the first few years as well. It certainly was a thing in the mid 2000's. Each department also had different standard uniforms too. Operations had the blue with yellow trim, cleaners had green or red shirts and food and beverage was blue and black.
One of the great things about Dreamworld was not having to wash your own uniforms either. You would go to work in whatever clothes you wanted, and pick up freshly laundered uniforms each day. Not sure if that's still the case or not (Movie World was the same, except you had to wear the "day uniform" to work and keep it on you in case you had to move to a ride that didn't have a set theme)
Hopefully with the majority of the decent management that was at Movie World in the mid 2000's now at Dreamworld, we might see something special for Rivertown (and future attractions) to really bring back that kind of sparkle.