How did the hagia sophia combine both roman and greek architectural elements?

Hagia Sophia was built under Justinian (Byzantine Emperor 527-565). Justinian is also known as Saint Justinian the Great in Eastern Orthodox Church. Because of him he demanded/ordered the workers to add columns (corinthian/hellenistic columns which is seen in Greek art). It was one of the largest churches around, a masterpiece.

What area are in blue