by default these special field values are stored in the keyword field.
You can change this setting in "Entry table columns" so that JabRef writes each special field as own field.
This data is stored in the bib file and should be displayed after importing. I think your colleagues then need to have the special fields columns enabled in their JabRef instillation, too.
Regarding colors: JabRef does not store the color name or color itself (e.g. red), but the number after the colon in the field __markedentry refers to the custom colors 1-4 from the settings.
The best way to ensure that everyone uses the same colors etc would be to export your preferences as XML file and give them to your people. In the XML file the colors are stored as RGB.