I'm trying to to teach myself to design gears for a hobby project, and I want to make a similar design. I typically use Autodesk inventor, but I was wondering if there was something better for this sort of thing. 
This is from this question.
It is conjecture based on my experience with the 3D modeling program known as OpenSCAD.
The colors of the components and placement are consistent with the program, as well as the background color. There is usually a set of axes visible with reference measurements, but those are easily disabled, allowing for a screen shot of this nature.
From the gallery option in the linked site: