As many correctly pointed out, Italians are a very diverse and vary population. Although the usual stereotype of Italian is white, brown hair and eye, it's not always the case. It's also true that we do differ based on where we come from.
Sardinians are very particular: you wouldn't say they are Italians. They're very similar to Middle-East people. They are also known for being quite short people, in average. There's an immigration story behind this.
Southerners, usually, are of the Mediterranean-style: white, brown hair, medium height (way shorter than European average, but similar to Spanish, Portuguese and Greeks). In Sicily, it is easy to meet people with a darker skin (Arab invasions say anything?)
Northerners are considerably taller than Southerners. It's also more common to meet blonde people in North Italy.
I come from a former Greek colony: people are mostly Mediterranean.