Just expanding on Graham's reply -
Keep in mind that typical printers rely on the paper color for white...
There is no such thing as "white ink" unless you have it custom-mixed in
commercial printing or specialized printers. In order to render white
standard printers apply no ink, so the white paper shows through. Likewise,
light colors are rendered by thin/sparse application of other colors so the
paper shows through - just less so than if white. Therefore, the darker the
paper color the darker the ink you have to apply to get it to show up well.
HTH |:>)
Bob Jones
[MVP] Office:Mac