I have a soft spot for black and white sketches with pops of color, like these ones by architect Mariano Recalde, who was interviewed about his drawings by the Tribeca Citizen:

Do you bring your sketchbook everywhere you go?
I try! I carry it a lot more than I actually use it, but being ready to sketch when you find something that you like is the first step. I have a small bag with my sketchbook and some markers that I grab every morning when I leave for work.

Read more at: Tribeca Citizen | The Sketchbooks of Mariano Recalde