Colour difference with layers

I've used the Snip It tool to grab a screen image and because it was large I've done it in 4 parts and save as jpgs.

By @WulfstanDesign

Windows Snipping Tool can capture your full screen as one screenshot. What happens when you try that?

Details here: 
https://support.microsoft.com/en-us/windows/use-snipping-tool-to-capture-screenshots-00246869-1843-655f-f220-97299b865f6b

Jane

@WulfstanDesign IF you capture the 4 screenshots in exactly the same way and process correctly then they should match (be sure Snip-it isn't doing any colour processing or correction.)

Next, upon opening Photoshop you assign your display's ICC profile to each, then convert to a workingspace, sRGB is likely an OK choice in this scenario.

I'd open the 4 images individually in Photoshop first (processing the colour as above) then make a new doc to fit all 4 and drag them into 4 layers, set the overlaps and flatten - but check they match before dragging. 

Let us know how it goes.

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management
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All the screenshots should have been captured with consistent colour.

So was it the processing into Photoshop that was inconsistent, such as selecting different source profiles or conversions etc?

First of all, make sure the file already has an embedded color profile. If it doesn't, all bets are off.

A screenshot is a special case. The numbers in the screenshot have already been converted by the color management system, from the original document profile into your monitor profile. The original profile no longer applies. Those recalculated numbers are sent to screen (thus representing the file correctly in the new color space).

So what you do is first to assign your monitor profile. Then you convert back to the original document profile.

They will now match perfectly.