Here's a lovely map, one of many combinations you can choose on a site called "Transparent New York" from the Skyscraper Museum. Here you've got topography in green, and then skyscrapers color-coded by era: 1893-1916 yellow, 1917-40 white, 1945-64 light blue, 1965-75 blue, 1980-89 red, 1999-2005 orange. Enjoy!