Fill colors not saving correctly. They change color upon reopening
 

In Excel 2007, when we select a row, column, or any cell, and fill it with
one color, when we reopen the document the color has changed. This is not a
drastic change, but it is still not the original color we saved it with. For
example, if we save in a light gray, when we reopen the document the gray is
a darker gray or a light pink turns a darker pink. All the colors seem to be
turning a few shades darker. Anyone else having this problem? Any
suggestions. I am beginning to think this is another bug in the 2007 office
suite, as I have already found another in Word 2007.