Lastly, discus - the most obvious option - rival many marines in color. They are not all that difficult to keep if you do your research and, perhaps, are the perfect stepping-stone towards going marine.
This is a cichlid too, except it's defeating the purpose. Discus like a heavily planted tank - hardly a marine-like setup. He wants lots of rocks. This means
rock dwelling fish. This is why African cichlids come to mind as the best alternative. Maybe I'm misinterpreting the post, but it sounds like he wants a marine-like setup, not just marine-like fish.