00, 33, 66, 99, cc, ffThese 6 X 6 X 6 = 216 are supposedly "Web safe"; however, Internet Explorer misrepresents some of these. These will probably become "safer" over time.
Be aware, however, that nothing can correct for monitors set differently.
In addition to colors represented by number, there are many names recognized by HTML that are not necessarily Web safe, but still fun to use, such as "BlanchedAlmond" and "PapayaWhip" "DodgerBlue," "LemonChiffon". Here is a link to a list of 142 color names with RGB values and swatches.
Try some of the Web safe colors by number and colors by name below. You will need to reset the page by using the "refresh" or "reload" button on your browser.