Edge group tabs color problem

When I maximize the edge window, I can't see the color for individual tabs in the tab group. (2nd image). Though is shows perfectly when I minimize. I tried recording it just now but I saw that the color is showing both in videos & screenshots too. So I took capture it on my phone instead (2nd image). It used to show a few months ago so think it might be a problem with my monitor? I have no idea. 

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