Printing colors on transparent sheet problem

Hello everyone,

I've got two problems, a pain-in-the-ass for the moment.
I need to do some presentation work using transparent sheets as layers.

1.
There's a color problem when printing on the transparent sheet. I must print
colored shapes on transparent paper which, after printing, will be put on
the top of a background and must hide other shapes behind. In CorelDraw I've
made them uniform colors and they hide the background layers. But when
printed on the transparent sheet, these colors become transparent and you
see the background. Could someone throw light about how could I make the top
colors print non-transparent?

2.
Also, I have a "white color" issue. I want to print white characters or
shapes and want them printed on a transparent sheet so that they appear
white when put over a dark background. In CorelDraw it works just fine, but
when printed on a transparent sheet, the white objects are just NOT printed,
so they don't appear. How can I make white appear white when printing on a
transparent sheet?

Thanks for any feedback,

BD