macOS Combo Box and Core Data

I am having a problem with my Core Data application, I have a combo box with several choices (eg red, green and blue), and want to be able to bind this to a managed object depending on which colour is chosen, is this possible?

Well I've kinda solved it by binding it to the "value" in the code, though it doesn't quite work as I'd like it to, oh well, that's life.