You might also try using the 216 color websafe colors pallette. However, there are discrepencies in color reading (as well as other things) among browsers and even versions of the same browser
To make sure a color matches, it's easies to make square or rectangle in PS and save as a 1 color gif. Then use that gif as the background image for the whole page. The size of such an image is quite small and does not hurt download time much. Depending on you web design app, you can make a small image repeat so as to form a solid background. PNG can also be used, but more browsers support gif.
As Jim Oblak said, make sure to disable any color management.
Using OSX 10.3.9 on a G4