Color is a surprisingly tricky thing. First-year philosophy students mull the idea that it's impossible to know if the red that I see is the exact same red that you see. In a more practical sense, a wide array of physical factors influence how we see color: Your shirt looks different in low light than in bright light -- or than in yellow light. More annoyingly for those who do graphic design for a living, the way you see colors on your computer screen is very different than how they look once printed out, particularly since it also depends on the type of material the color is printed on.
In the design world, there's a color system called PANTONE that codifies particular colors in order for designers to ensure that the IBM blue they used to design the ad on their computer is printed in the proper, brand-identifying shade of red you associate with the computer brand. (IBM's PANTONE color? 2718.)
The government has a similar system for assuring color consistency. As you might expect, it has the much more bureaucratic name FED-STD-595.
There are 650 different colors that fall within the government's approved guidelines for color. (You can view them all here.) They're numbered, in the same way that PANTONE numbers its colors, with a three-part code. The first of five digits indicates whether the color is glossy (shiny), semi-glossy or flat. The second digit indicates the color group -- one of nine options that broadly describes the color ("brown," "green," "fluorescent"). And then a three-digit code indicates the specific color in that group. The General Services Administration offers specific guidelines for the color content of each of the 650 colors, including variants for its use in daylight, indoor fluorescent lighting or an incandescent bulb.
In 2011, Graham Beck outlined the history and evolution of the government's color palette. It's a great read and well worth your time. The short version of the story is that World War II's huge demand for materiel prompted a need to standardize particular colors for particular uses. The system has been refined since then; the most recent iteration dates to 2008.
Beck's piece also articulates some of the specific colors currently used for specific purposes within the government. In the interests of testing your knowledge of your government, we've adapted this overview of those colors into a quiz. If you miss any of them, one of two things happened. One option is that you don't pay much attention to the infrastructure around you.
The other is that your screen isn't calibrated correctly.
Which of these is the official color for a mailbox?
Which of these is the official color for a highway sign?
Which of these is the official safety orange of OSHA?
Which of these is the official color for Forest Service signs?
Which of these is described as "Public Building Standard"?