Hey all - I was just given a V3 ST hub, but it is stuck at what I’m guessing is the blinking magenta/purplish light. I reset it based on the Support instructions but it didn’t seem to have any effect. Anyone know anything about this? This device is new to me as well.
If it was blinking magenta, it was trying to download a firmware update. If you reset it in the middle of that, you may be hosed and need support’s help to get things on track again. 
For now you can just leave it plugged in and see if it completes the update.
https://support.smartthings.com/hc/en-us/articles/205956920-What-do-the-LED-colors-on-the-Hub-mean-
Hey there! @PMT223, You can also force a reboot of the Hub to ensure that it resets and by allowing the blinking magenta process to complete it will update to the latest firmware version and you will be all set to begin adding your devices and enjoying your new experience. As you mentioned you have already reset the hub, so as JDRoberts mentioned you should contact support to monitor the process as you set up your V3 Hub.
Please read the official knowledgebase article linked to above. It tells you specifically not to interrupt in the middle of a firmware update or you can brick your hub. 
If you need help with A hub stuck on blinking magenta, you should contact support.
How do you contact Support?
In UK - thanks. App help support non responsive. More help here - thanks.
Hello @pmt223. Were you able to figure this out? I have two hubs that went out in the middle of the night and they are both magenta. No power failure or anything, they must have just received a bad update. Were you able to get yours going again?