Sorry justaskjoe, but the black diamonds are every 19.2''. 16'' centers are represented by a red rectangle. The black diamonds allow you to save one joist or stud every 8'. If you use the black diamonds, you will have 5 equally spaced studs every 8' instead of 6 when using the red rectangles. However, I'm not sure how efficient this is considering any sheets I've seen are marked for 16'' or 24'' centers, so although you could save money by purchasing less joists, you would spend a lot of time marking your boards every 19.2''.
http://www.lowes.com/lowes/lkn?action=howTo&p=Build/TapeMeasure.html

These diamonds represent 16 inch centers for laying out a stud wall.