|Colorized by Redditor mygrapefruit.
[ Update: ] How she did it: Photoshop CS 5, wacom tablet. Brush tool with Mode set to "Color". Sometimes I made finer selections in quick mask (press Q) to easily colour an area. I personally find this easy to do, it is only time consuming, especially if you feel the need to research the actual real colours (I found some vintage postcards of times square to figure out the colour of the buildings and some signs). The rest of the colours I guessed by using common sense.