Only been to Santorini in the summer, and then it’s brown.
Atlantis is described having distinctive black, red and white stones – I can confirm the presence of lots of walls made out of these three colours.
Vegetation is also quite distinctive, especially vineyards… most vines are sort of long creepers – on Santorini they are bushes!
Buildings are standard whitewashed flat roofed Mediterranean buildings. Domes, lots of doors, windows and decorations are often a bright blue.
Streets in the towns are narrow – actually, the width is designed so that two donkeys can pass each other! Donkeys are still a major form of transport today. Excavations from the time of the eruption suggest a similar setup then.
Although everything described above is Santorini today, back in the days of Atlantis things were probably not much different. However, some aspects of the terrain are more recent. Modern day Santorini (and lots of other Mediterranean islands) are covered in prickly pears. These were introduced from the Americas a few hundred years ago and are especially useful for making one of my son’s favourite liqueurs. The island also has lots of oranges, lemons and pomegranates. These have been gradually spreading through the Med over the last few hundred years but I’ve no idea when any of these became established.