Yup. Use a web safe pallet. But then, of course you will have, as someone said "five shades of green, and all of 'em would make a lime puke!"
Further if you try bringing up the web site on different monitors, you will notice even wider variations in color.
Nothing much to do about it, just keep it in mind in the design phase. Oops! I've joined a club that'll have me as a member?