Not green is disconnected from any access point. The radio is still active, and listens for SSID broadcast, and advertises a MAC address, for possible connection handshakes from access points that are listening and active, but do not advertise presence and require users to request by name.

Not green AND CROSSED OUT means the radio is actually turned off, and is supposedly neither listening nor broadcasting, if state of the settings applet is somehow more trustworthy than the state of the control center’s slide-out drawer widget.

Note that other non-apple handsets might just be doing whatever, unpredictably.