SilverWook said:
The Imperial uniforms were already present at the end of Episode III. And we have no on-screen evidence what was worn before the Clone Wars started.

Did the Republic even have a fleet before Episode II?

There were two pilots on the cruiser that delivered Qui-Gon and Obi-Wan to the Trade Federation battle station in the first scenes of Episode I. We got a brief glimpse of the pilots from the front: they wore a navy-blue version of the Imperial uniform.

According to various books, the ship: Radiant VII belonged to a fleet of ships used by the Republic to carry diplomats around the galaxy.

.. back to the series:

I was able to see the first two episodes on-line on Cartoon Network's website, and I liked them!
Then Cartoon Network cut us non-USians off from seeing them (any episode), which is something that puts me off.