You might try:
1) In XL, turn off the gridlines w/Tools>Options>View>Gridlines
2) Before selecting the Edit > Copy command, hold the Shift key; Copy
becomes Copy Picture;
I believe this won't allow a paste link in XL though

AC,
I know this is going to sound totallly off the wall, but the problem is most
likely that your default printer is a black and white printer. What you need
to do is to add the drivers for a color printer and install them. (You don't
need th printer, you just need your system to think one is there.) Before
you do the copy and paste, make the color printer the default printer. When
you are done, change it back to your real pritner. You should then get the
colors you are looking for.

Kathryn Jacobs,  Microsoft MVP  OneNote and Powerpoint
Author of Kathy Jacobs on PowerPoint - Available now from Holy Macro! Books
Get PowerPoint and OneNote information at www.onppt.com

I believe life is meant to be lived. But:
if we live without making a difference, it makes no difference that we lived

Excel in PowerPoint is a major pain.  The best way to bring it in is as a
bitmap.  Make your selection and paste it as Device Independent Bitmap.  If
that doesn't look right, get the Excel sheet full screen and hit ctl+prt
scrn, then paste the screen grab in your PPT and crop the control areas.  If
you need interactivity, link the bitmap to the original XLS file.

Steve P.