It can't be done with a conditional format. But it's easy to do with a few clicks, and I think you can record a macro to automate it, although I didn't try that. Here we go:
- Home >Search and Select > Find
- In the Search and Replace box click Options, then click Format.
- Specify the font color you wish to give a different background.
- Back with OK.
- Click Search all.
- In the bottom of the dialog window you'll get a list of all cells with that font color. The first one is selected.
- Using the vertical slider, go all down and shift-click the last line. This select all cells that have been found (can be an uncontiguous selection).
- Click on the background color icon in Start (or use the dialog box launcher in the Font group to format the selected cells with the right background color).
But as Bob wrote, it's still easier to instruct the person making the spreadsheet to make it more printer friendly. Then this would be a one-time operation with no need to record a macro.
An interesting lesson, by the way: your subject line was about conditional formatting and with that tool it isn't possible, so the answer was "no". A more open question would have been "How can I give all cells with a certain font color a certain background", or somewhat more general "How can I select all cells with a given font color". If you don't know how to do something, ask if it can be done or how to do it, and don't steer the people wanting to help you in a direction that could be wrong, and in this case was wrong.