Re: Designing Interstellar Cultures
Oh sure we can...bearing in mind that we don't get an indepth look at yer Klingons and Romulans all that much. For example there was a TNG episode where one of the Klingon worlds was rebelling, but we never even met the rebels and found out just what their beef was. Later on I saw a world of pacifist Klingon-Romulan hybrids. Don't get much more different from the supposedly homogenous Klingon culture than that. But in part it's like looking a face of another race. You have to spend a lot of time looking at the faces of a visually distinct ethnic grouping before you stop thinking how different they look from your lot, and start thinking how they look different from each other.
But apart from that, another consideration is that actual cultural differentiation requires communication barriers. Establish your colony on Mars but give them 24 hour access to all those Earth TV channels, and they will not be a terribly distinct society from the Earth society that founded them. They'll talk pretty much the same, and they'll imbibe the same attitudes about life and right and wrong.