I noticed a strange thing here with my alliums. the purple color lasted only a short day and then turned green. can't figure why??
Was it hot? If so, they probably just did their thing really fast, and are turning into seed heads.
Same thing often happens here with early June perennials, like my lupines and Dutch iris. A heat wave hits, and they come in go in about one to 2 days.
While you might find this nuts, I used to work as a florist, and I've been known to spray the forming seed heads with purple floral spray paint -- gives a lot longer show in the garden, and almost no one knows its fake. There are many shades of purple (Design Master is a good brand) so its easy to match, or you can be creative and totally change the color if you want to. Nuts, I know.