It would appear that a color style has been applied to data inside the field. Styles applied directly to the data supersede styles specified in layout mode for the field object used to access that data.
You can use the TextFormatRemove function both to clean up existing data and to prevent data from being either pasted with styles or to keep users from styling the data in new data.
Replace field contents can be used with this function to remove such styles.
TextFormatRemove ( self ) is an auto-enter calculation you can specify for a field to prevent this from happening in the first place.