F.lux with 2 external Mac displays
I use a MPB circa early 2015 with 2 external displays. One is driven directly from a dvi display port, the other from USB to a DisplayLink to VGA. Flux controls the first display, but not the second. This makes sense because VGA doesn't support a color control protocol. I deal with this by changing the colors on my second display by hand twice a day.
I'm hopeful that some new devices on the market that use the Thunderbolt protocol will fix this problem. They include the Elgato Thunderbolt 3 Dock and the StarTech Thunderbolt 3 Docking Station. But they're expensive, over $250. Would driving two displays through one of these devices enable Flux to control the color of both of them?
@arthur.goldberg I misspoke.
Display 1 is driven dvi - StarTech adapter - VGA: Flux controls it.
Display 2 is driven USB - DisplayLink adapter - VGA: Flux does not control.
My displays support DisplayPort and VGA inputs.
I found an INEXPENSIVE solution: use a min-DisplayPort -> DisplayPort cable. BOTH external displays are controlled by F.lux.
I discarded the USB to a DisplayLink to VGA cable, and replaced it with a mini DisplayPort to DisplayPort cable. You can find cheaper cables elsewhere. The Thunderbolt port on a Mac is a Mini DisplayPort.