It’s actually CTRL-ALT-arrow. I’ve got two monitors so I thought I’d try out one as landscape and one as portrait, but I find the colours change when I rotate the monitor. Back to both on landscape I think.
I hope this isn’t too off-topic, but has anyone else experienced a disconcerting feeling that a 16:9 or 16:10 monitor is too tall (versus the width) when run in portrait mode? I bought two high-end 23" IPS displays a couple of years ago to use this way for coding, but found the aspect ratio oddly disconcerting when turned on their sides. It’s an optical illusion, of course, but the displays just look wrong to me in portrait mode, to the extent that I can’t stand to use them in that orientation. I’ve settled in with landscape mode and resolved to use my page-down key a lot more often.