I've been using photoshop for a while now on my MacBook Air (2013?) and have recently added an external monitor (an HP 24m) -- the problem I'm having now is that randomly the image will flicker in between color - sometimes it is a warmer or cooler version of the image and I can't seem to find any information on how to fix this issue. If I try to maximize the window, the color will shift and again if I come out of full screen mode. And if I working on a layer using the brush tool, the image will shift between warm and cool if I move around the image to get to a different spot when I'm zoomed in. It's driving me crazy and it makes me feel like all the work I'm doing could be on the WRONG version of the image and it'll change again at some point. Any and all advice would be so helpful!
You are likely exhausting whatever limited hardware acceleration resources such a weak portable computer offers plus there may of course be additional issues with the external connection, color profile usage. This may be fixable by playing around with your system's graphics settings and the monitor's menu like e.g. disabling HDR emulation and enforcing an older HDMI compatibility mode, but otherwise there may not be much you can do other then checking for a defective cable. That and of course playing around with the hardware acceleration settings in PS itself. Using a different drawing mode and turning off some of the fancy options may improve behavior.