I'm using Illustrator in CS2.
I have a logo that sits on a white background. I need to distribute it for a variety of uses and one of the formats I've selected is jpg (principally for people creating desktop documents and making presentations). Because it's intended mainly for print use it's in CMYK mode - and the colours of the logo certainly come out differently in RGB mode whether on the screen or on paper.
The problem is that I've discovered that white in a CMYK jpg actually shows up as a very faint grey on the screen when imported into Microsoft programs such as Word and Powerpoint (unfortunately I only have Adobe and Microsoft applications so I can't tell if it's a Microsoft-specific issue). My own tests indicate that it's only an issue on the screen and that it prints in white as it should, although a user has said that he can see the edges of the "white" when printing.
You can see what I mean if you open a new CMYK document in Illustrator, add a white rectangle with no border, export it as a jpg and import that into Word. If you do the same but set the colour mode to RGB the problem goes away.
If it weren't for the colour shift in the logo I'd simply save it in RGB mode but the whole point of publishing the logo and its accompannying branding rules is consistency. I don't suppose there's a lovely little button somewhere in Illustrator that says, "Make white white," is there?
Simply eliminate the white shape you are using for the background. Since jpeg does not support transparency the back ground will be an opaque white anyway bit will have a color wall or white unless you adjust it as a jpeg image in photoshop or other program.
But using a jpeg for print is not the wisest of choices.
See the duplicate thread.