I did a detailed investigation of the glowing blue mouse cursor issue
I recently upgraded my personal machine from Mojave to Catalina 10.15.4 and ran into an issue on the built-in display where the whole screen except the mouse cursor is color shifted. The issue occurs with both f.lux and with Apple's built-in Night Shift, but only with the factory display profile on a MacBook Pro (13-inch, Mid 2012). It does not occur on an external display, or on the built-in display when using a calibrated profile or any display profile other than the factory one. The issue also does not occur on a MacBook Pro (Retina, 15-inch, Mid 2015) that's also running 10.15.4.
As I'm not particularly knowledgeable about the vagaries of ICC color profiles, I'm stumped.
I submitted item FB7642867 to Apple and wrote up everything I know about the issue at https://mplough.github.io/2020/03/28/blue-cursor.html.
Perhaps someone who knows more about color profiles will be able to take this further and figure out what's going on. At this point I really don't think it's a bug in f.lux but perhaps f.lux could work around the issue before Apple's fixes its own Night Shift?
Happy to provide more info as needed.
A work around that I discovered:
System Prefs > Energy Saver > turn off 'Automatic graphics switching'
I believe Linux has the same problem. I don't know if f.lux has a Linux version or not, but I use a similar program called redshift, and it has this mouse pointer issue. The little bit of research I did indicated that it is a very difficult problem to fix, so I just live with it. A minor annoyance.