I'm pleased to confirm loco_diablo's observation:
The inverse-video night mode hack is working with firmware 4.2.8110 on the classic 6-inch Aura (version 1) *if* you use the experimental version updated for the Aura One; a long press of the regular Aura's light switch toggles regular and inverse-video modes. The correct version of the hack is here
in message 610 of this thread.
THANK YOU!