You may have never even seen this, but for those who watched broadcast television before the days of cable and cord-cutting, these color bars announced the end of a long day. As it turns out, every aspect of the TV color bars are intentional. Here’s more from The Verge:

These test bars, throughout their evolutions—with the most recent occurring in 2002 to account for the HDTV switch—remain important in the television industry, as they allow engineers to adjust color schemes to correctly match what’s on the screen and modify accordingly.

But, thinking bigger picture, they represent some of the first electronically produced graphics ever displayed on a screen—a pretty significant development in a world where graphics are everywhere. (Graphics, while a fundamental part of computing today, didn’t become mainstream on computers until the 1970s, when terminals transferred from printers to monitors.)

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