Web Safe Color Chart
This web safe color chart contains the 216 hex colors from the web safe palette.
Web safe colors were popular in the late 1990s when most computer monitors were 8-bit and could only display 256 colors. Only 216 of these would look the same between different computer systems.
Web safe colors aren't as important as they used to be. However, the web safe color chart is still a good way to come up with quick colors for a project.
Here's more about web safe colors.