There are an insane number of different stylings and colourings of astromech droids in the various R-series. Generally, pilots had their own R-series droid to handle the mechanical stuff necessary to operate their ships. Obi-Wan's was R4-P17, as seen here.

Unfotunately not seen in the movies is Mace Windu's droid R4-M6, which is quite definitely and remarkably purple to match his lightsabre.

Transcript

Obi-Wan: I don't have much time. I think Jango might try to blow up my ship. Can I borrow a ship if I need to?
GM: Actually, the Kaminoans aren't a space-faring race.
Taun We: Taking off would make our necks snap like a twig!
Obi-Wan: I see. So, my ship and Jango's are the only ones on this whole planet?
GM: The only space ships, yes.
Obi-Wan: Hmmm. Convenient.
{walks out to ship in the rain}
Obi-Wan: R4, open a connection to the Jedi Council.
R4-P17: {GM} Uh... nipa-bing whree... ziku kabading.
R2-D2: What? Your hovercraft is full of eels?
Obi-Wan: I search the ship for eel-based traps.