This would be very easy in FMP9 or higher as you could use conditional formatting. However, since you are on an older version, you will have to use some trickery. You can use a calculation with container result to display a colored image in the background of your field usually stored in a global container field. As for the text coloring, you can use an auto-enter with calculated result using the TextColor function . Make sure that 'Do not replace...' is unchecked.
Here are some links to some old posts that explains it.
Thank you, thank you! I just read the links and applied it to my DB. Wow, you just saved me many hours of frustration! Many Mahalo's!!