Compression doesn't change colour, but colour settings do. Any particular reason you are using such ancient software - it doesn't have colour control like modern apps.
As Test said, Pagemaker has no real color control, add to that some generic online converter and what do you expect?
The best way around is to find a designer that can provide the required file, but if the printing site only accepts jpg and tif (not tip) files, don't expect much even with a better designer.
Thanks for the information. Sadly, I think up the proverbial creek with a paddle <g>. I can't explain why she's using PageMaker, other than it's what she has, as she primarily does brochure/invtitaion layouts rather than actual graphic design.
She's laying out wedding shower invitations, place cards, etc that showcase various photos of the bride and groom, and our idea was to print them on fabric so I can make a companion quilted table runner. Oh, well.