How to set Different Icon for different Color Theme in UWP
I'm afraid you can't set different application icon for different theme. You could only update icon's background, for more please refer this document.
Form version 2004 h2 blog.
Theme-aware tiles in Start – The redesigned Start menu has a more streamlined design that removes the solid color backplates behind the logos in the apps list, and applies a uniform, partially transparent background to the tiles. This design creates a beautiful stage for your icons, especially the Fluent Design icons for Office and Microsoft Edge, as well as the redesigned icons for built-in apps like Calculator, Mail, and Calendar.
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