All of them. Except many of the slaves were probably Moors or Egyptians. But all of the citizens would have looked much like people from Northern Italy do today (blue eyes, blond hair).
The center of Italy was populated by Etruscans (which had dark skin and hair) with a history which goes back to 900 BC, and Rome was founded about one or two hundreds years later.
Since Etruscans were absorbed by the romans only later, in 386 BC, and considered that some of the seven kings of rome weren't even roman (Tarquinius Priscus was half greek and half etruscan, and both Numa Pompilius and Ancus Marcius were sabine - another dark haired culture derived from samnites - to name a few), you can already imagine that the population was heavily mixed.
Given the complex trading routes involved, there was also a strong influence from greece, so that historicians never consider the existance of a real italian race. Later even north africa added to the equation, resulting in a complex mix-up of cultures, even though the latins themselves which inabithated the tiber were from the balkanic area.
Even today if you visit northern Italy you would be surprised to know that there aren't as many blond people as you may expect (blue eyed too even less)... that's an extremely simplistic view, considered that most of the european cultures mixed in that region in the beginning of history, when racism wasn't a decisive factor when dealing with legacies and politics as it was in the medieval era.