Font-Color Change

When I receive a response to an email that I originate, the signature block
of the person's email responding to mine switches to a
light yellow such that it cannot be read. If I highlight the entire email, I
can change the font color to black and then it's readable. Why is this
happening? What setting needs to change so that when a persons responds to
my email, it appears as it did when I sent it? I have already checked my
settings under Tools-Options-fonts and I have selected "always use my fonts"
which are a green in color.
Thanks in advance. Using Microsoft Outlook 2003, Word as the editor.