I expect a colour to look different on one display to another, due to hardware differences. I expect that my OS (Windows 11) can compensate for this difference in software, with the use of Colour Profiles. This compensation should then mean that colours match to the human eye as closely as possible, between the two displays.
However on my clean install of Windows 11, the opposite seems to be happening. The hardware seems rather well matched to my eye (as per my testing below), but the Windows colour profile being applied to the external monitor seems to cause the colour to change to something that does not look right to my eye.
I have two reasonably good quality displays (Dell XPS17 9700 4K and Acer BM320) and if I start to drag a window so that its title bar spans across both, the colour (e.g. of the title bar of that window) looks very similar across both screens.
But if I continue to drag the window further, two things happen: the window resizes and the title bar changes colour significantly.
I understand that Windows is essentially registering the window to the adjacent monitor and attempting to match its resolution (hence resize) and colour (hence change in colour).
I believe this means that the issue is completely independent of any monitor hardware settings (e.g. brightness of laptop screen or external monitor / gamma / contrast / selectable hardware colour profiles buttons on the monitor)
If I run a colour picker and point it at the background colour of a website, the HEX colour returned on one monitor is different to that on another. For example on this website the dark blue background registers as #102236 on the external monitor and #182235 on the laptop display. The source code of that site indicates the colour should be #102236. Can someone explain this to me in simple and clear terms?
Bonus question / additional confusion
When I recreate that background colour in Photoshop using the gradient fill tool and setting the colour to #102236, the colour looks significantly different in Photoshop to the colour displayed within Chrome web browser, even though the native Photoshop colour picker tells me they are exactly the same. This is when working ONLY on the external monitor. This even shows in the screenshot I have taken, see below. The bottom left colour is the website and the bottom right is my fill colour in photoshop.
However I don't believe it's related to an issue with colour profiles. Because when I run the colour picker tool again on the fill colour I just created in photoshop, it shows as a different hex colour to the one I set in the dialog box.
Colour Management Settings in Windows
Under the devices tab, there is a profile associated with the Dell 4K screen, that profile is called 14D6 (default), filename is Dell_XPS17_9700_UHD_SHP14D6.icm. There was previously no profile associated with the external Acer BM320 monitor, until I pressed the calibrate button and went through a calibration wizard (which barely changed any of the above issues).
Can you help?
How do I resolve the above? I just want to know how to reliably reproduce colours, and also have them look the same. Or if that's not possible then I'd like to know what workarounds I should make, and what expectations to set with my clients.