Colour Palette Problem
 

On my Colour Palette, the red option turns to grey.
When I hover over where the red colour should be with my mouse, it says that
it should be red, but its grey.

This happens occassionally, but will stay in the incorrect format until I
reboot.
I use a lot of excel documents throughout the day and often these have come
from outside sources.

My assumption is that within one of the workbooks I use, there must be some
VBA code that changes the Colour Palette.

Has anyone else suffered the same problem?
Is my assumption as valid one?
Can anybody advise me on this problem?

Many Thanks,

Simon