One orange, one white electrode - dead tube, Emitter one one of the electrodes has expired.
As for the blackening issue, not *always* what happens. Especially in the larger tubes where electrode shields are often used to prevent the sputtered electrode material from being able to contaminate the phosphor coating inside the tube.
Just make sure that you remove the starter from that lamp (or even better, the lamp itself), as this cycling behaviour stresses the ballast - especially if the starter contacts stick shut (which they probably will do eventually if it keeps cycling). And sitting like that will almost certainly overheat the ballast. Probably won't actually damage it (most modern ones have built in overheat protection anyway) - but obviously ain't good for it at all, and could very possibly present a fire hazard.
