Very odd. I installed flux on my Mac and at first didn't like the effect (the screen went yellow) so I hit the 'Disable for an hour' and didn't think anything of it.

So, a couple of days later I remember I installed it, the screen looked 'normal' so I assumed it was still disabled, but no, it was actually running and upon hitting the disable button again the screen went 'blue', so I re-enabled it. I actually really like the effect. It does still look a little yellow to my eyes, but in a nice 'warm' way.