Hi Gregory!
So sorry for the long delay in replying! Your message was stuck in our Google Groups spam folder!
The Excel or LibreOffice "Fill" color of a cell will be lost, since OpenRefine does not retain all of a Spreadsheet's cell metadata (fill color, comments, etc.)
Since OpenRefine is a data tool, it's mostly concerned about the data (and it's format or structure).
Would "could" in theory retain a "fill" color on import and conceivably retain it on export.
But that would be an extremely low priority for us. You would be the first to ask for that feature!
I would say that this falls into the scope of our "metadata" plans for Columns and Cells.
Some of which has been under much discussion over the past 2 years.
Here's the "metadata" issues
I would be super interested to know more about your usecase on retaining "fill" color and why it's important for you...as well as knowing how on export you would typically use the "fill" color in other programs and what those are, etc.
Can you tell us more?