• The first character design, on the left, was rejected because it was felt that the Blade Runner influences were too obvious, and because some people felt it would be easier to relate to a human rather than a Zabrak.
• The second design was a bit too effeminate and too pirate-like.
• The third one was too stuffy and formal.
• The fourth one, however, nailed the character - everyone was happy with this design, and this how Col Serra appears in the final game.

Via Star Wars