The Federal Standard color system, officially named Federal Standard 595B - Colors Used in Government Procurement, is a United States Federal Standard, issued by the General Services Administration. The standard is also widely referred to as FED-STD-595, FED-STD-595B or FS-595B (the suffix B corresponding to the current revision of the standard).
The Federal Standard 595 color system provides means of comparing colors visually. It has its origin in the US military complex and is still used there as the primary source of reference for military paint. Today, the standard is widely used for choosing paint not only for the military applications, but also in government procurement, consumer and industrial products.
Each Fed-Std-595 color is identified by a five-digit code. There are 611 color codes in the standard, representing 357 unique color shades. The difference between the numbers depends on that many colors are represented in the standard with different grades of sheen (gloss, flat), giving multiple color codes for the same basic color. See Understanding the Color Numbers - Federal Standard 595B Color Numbering System for further reading about color codes and their significance.
Fed-Std-595 is one of the very few Federal Standards which is not being distributed digitally by the GSA, General Services Administration. There principal reason for this is the intrinsic difficulty of rendering real-world colors exactly in the digital environment. See Accuracy of Online Color Samples for further discussion on this topic.
Thus, the Federal Standard 595 comes as a set of color chips which can be used for exact color matching and color quality control. For information on how to purchase these, see Obtaining Hardcopy Federal Standard 595 Color Chips.
Within the limitations of the digital color rendition, this very site will provide you with the comprehensive computer representation of the standard. The idea behind colorserver.net is to allow designers to 'color match' and work with specific colors digitally, usually before a design enters production stage.
Many of the colors in the Fed-Std-595 range are also available commercially as pre-mixed paints, especially for general use and small applications such as modeling. Specialized paints can generally be ordered in and mixed to the exact shade, but if your paint supplier does isn't familiar with the Fed-Std-595, color chips are still the way to go for mixing an exact shade.