510 is a great choice but it does have short battery life w/ standard
batteries (2-3 hours at most for a light or moderate vaper). I use a charger at work and I also have a PCC. 510 is the most supported threading. They also have mega xl
batteries that last 60% longer and make it 138mm w/atty+cart or 128mm w/ a standard carto. And I recommend manual
batteries. If you want to be able to refill cartos and drip with a drip tip without risking killing your batteries, get manual batteries. Manual batteries also won't turn on by accident from wind or vibration. And I think they are less work.
That Cignot black/purple - it could just be a purplish blue. All of my black 510 batteries have dark blue LED. As does my midnight blue 510 battery from VaporLeaf.com.
My Vapor4Life (not 510, is KR808D-1) lavender battery came with a pink LED.