Update: There seems to be a problem with printing my color sheet, but I have no idea what it is. I received an email today asking for a JPG copy of the original bitmap file, and, if possible, the Excel files used for the artwork. I have no idea why either would be needed instead of a PDF.
The JPG was no problem. Most of this sheet was done with either "throw-away" Excel files, where the text was altered enough that there was no point keeping the original, or wasn't made in Excel to start with.
The only thing I can figure out, and the email gave no clues, was that the combination of white and other colors requires a file format with separate color layers. They do require that, in a mixed sheet, any white be assigned a color not used elsewhere, which they will convert to white. If the combination is the problem, I can easily alter my sheet, replacing the white portion with black/color material, but it could be an issue for those wanting color+white heralds.
Or, that might not be the problem at all. As I said, there was no hint of why they wanted the files.