After examining the ep 5 shot by shot changes on Star Wars.com I had expected to see a blue R2 in Star Wars too. (but he's only sometimes blue.)
R2 is blue when shown though the rear window of the cockpit of Luke's X-wing.
(for instance after Luke hears Ben's voice telling him to trust his feelings.)
When shown sideways he is black.
(After Luke says: "Red five standing by", or later when R2 is repairing the x-wing.)