Web-safe colors
A set of 216 colors from the early web that displayed reliably on 256-color screens.
Also called web safe colors, web-safe palette, browser-safe colors
Web-safe colors are the 216 combinations made from the RGB values 00, 33, 66, 99, CC and FF. In the 1990s they showed consistently on screens limited to 256 colors.
Modern screens show millions of colors, so the web-safe palette is no longer needed, though its tidy codes like #3366CC are still around.