http://www.excelisys.com/filemaker-tips-tricks-demos-downloads.php (look for "color picker demo")
to apply the color
Is there a way to apply the formatting to a field outside of the conditional formatting
I can think of a couple of ways of accomplishing this.
(A) Overlay on top of TheOriginalField a calculated field that uses something like
TextColor(TheOriginalField; RGB(userPrefRedVal, userPrefGreenVal, userPrefBlueVal)
(B) Limit the number of available colors to something you can deal with, e,g. 8, and then "Add" additional conditional formatting rules to the field to change the text color. Each rule will select a different color.
Only one of the colors will be selected because it matches the condition satisfying the user's preference. Each conditional formatting calculation could be a simple equation depending on how you have your user Preferences accessible from the current context.
userPreferenceForThisItem = ThisSpecificColorCode
Both methods are a bit tedious if you have many fields to color.
You may find it easier to use method (B) on a single background element that lies behind multiple fields that would be color coded the same.