It's entirely possible it's part of a government
cover up.
No, really lol, there's a built in program in your
scanners at home which is designed to recognize
the colours in the dye of paper money. If it
detects these colours being scanned it'll
automatically replace them with a different colour.
This is apparently to stop people from scanning in
money for forgery purposes. So to get those actual
colours on the cel showing up you'll have to
manually paint them in unfortunately >_<

It's a common problem with Sailor Moon cels as the
colour which gets replaced shows up a lot apparently.

*This information brought to you from the Otakon
2004 Cel Collectors 101 Panel*