Overall, Greece has a pretty relaxed dress code and no one really bats an eye if people wear revealing clothing. This is especially true for the summer and in beach towns, it's very common to see women and men walking around in bathing suits and short shorts. The one thing that you need to be careful of in Greece, is how you're going to dress when visiting a monastery or church, and this applies to men and women. I recommend covering your shoulders, and wearing something that is long enough to cover right above the knee, or even below. It's easy just to bring a shawl and you should be fine! It is unlikely that someone will point it out or complain, it's just a matter of respecting the dress code.