.STL is a computer file format, specifically designed to capture a three-dimensional model of an object. This kind of file format is frequently accepted by 3D print services as a way for you to tell them precisely what to print. If you were to examine a .STL file closely, you'd see that it is simply an enormously long list of triangles that comprise the object's shape.
The basic .STL format unfortunately does not include any information about the object's color - it simply describes the shape. However, there are two variations of .STL that do include color information - but they are incompatible with each other and also incompatible with the original .STL format. As a result, color is often selected not via software, but instead by loading the printer with the desired media color.
.STL is typically produced by a CAD (Computer Aided Design) software package, such as SolidView. There are other software packages used to develop STL that we will describe in a future post.