For those who haven't never heard of f.lux before, here's a brief description via Wikipedia.
f.lux is a cross-platform computer program that adjusts a display's color temperature according to location and time of day. The program was designed to reduce eye strain during night-time use and reduce disruption of sleep patterns.
I propose adding flux as a synonym for f.lux. While it's not a particularly popular tag, it does have a few questions. Intuitively, most people asking questions wouldn't think to try using the f.lux tag unless they specifically remembered the program's bizarre spelling.