The vector file was built with 3 colors: 1. tan, 2. black, 3. red. The gray is a percentage of the black color and can be printed using black ink and "halftone screens". For processes which do not use halftone screens this would be considered a 4 spot color vector illustration: 1. tan, 2. black, 3. red, and 4. gray.
Before online printing exploded as a convenient and inexpensive venue for printing full color, many small printers only had capabilities for printing 1 or 2 color pieces and these were much cheaper than "full color" or "4-color-process" printing. Now most printers can pretty much print anything but there are a lot of processes that still require simplified illustrations with limited amount of colors. Printing on coffee mugs for example (although there are companies like Walgreens that can print a full color photo on a mug), vinyl-cut-stencil-like signs also need limited colors, and the embroidery process are a few that come to mind. Engraving and etching will need black and white only vector graphics - no color.