However, the point of f.lux is to give you the luxury of being able to eliminate alerting levels of blue light coming from your monitor so that you can still use your computer right up until bedtime without your computer being responsible for undoing any work you're doing with avoiding blue light from everywhere else in your home.

So, perhaps what you can do is let me show you how to prevent f.lux from starting with Windows (you have to make a simple change to the Registry). That way, you can launch f.lux whenever you want to use it.

Or, you can just set f.lux to 6500K all the time and then you can just manually change it to a very warm non-blue non-alerting color whenever you need it.