Phosphor

Hmmm. Maybe my eyes weren't deceiving me last night. The night sky at home is measuring 20.66 mpsas (normally 21.0) and the sky is grey with a purplish tinge, just like at the new property before I fell asleep last night. I measured 21.15 mpsas (normally >21.60) there around the same time.  The sky was nearly inky black last Saturday night. 

Moonrise is well after midnight and it's well past astronomical twilight, so those can be ruled out.

@Stone Cold Steve Tuna, I think the increased solar activity is responsible for this. 

https://www.spaceweatherlive.com/en/news/view/396/20191022-coronal-hole-faces-earth-g1-watch