I have recently upgraded to an iMac (Retina 5k, 27-inch, 2017) that has High Sierra (OS version 10.13.3) installed. I have an Asus monitor that I used with my old iMac and had no issues. Ever since the upgrade (usually not more than once a day), the second display will suddenly turn blue:
The only cure I've found is to disconnect the screen and reconnect it. Another similar problem I have with this computer is that my headphones are not recognized all of a sudden and I have to unplug and re-plug to resolve this.
I have a feeling there is some sort of software glitch as both the monitor and headphones worked well on the old computer. I would appreciate any help resolving this.
Update: Ever since I've reset my SMC 2 days ago, I haven't seen the "blue screen" (thank you @howdytom), but I am still not sure that this a permanent solution. As I am using a cable that was given to me by the IT department, I am not exactly what adapter it is. But here is a picture of it:
BTW, after I disconnected the cable the headphones were not recognized again and I had to plug and unplug them.