On macOS with Edge Dev (78.0.268.1), it seems that the text highlight color does not use the color specified in System Preferences > General > Highlight color.
Instead, the color is a strong blue as pictured below.
It seems that the Address Bar is affected by the highlight color. I tried changing the highlight color to purple and the address bar reflected the change, but not the main web view.
Note: This is a repost because the original one was removed, sorry :|
After further research, I found out that the opposite happens on Windows: the web view's selection color is the typical one (same as Google Chrome), but the address bar uses a strong blue color (although this one seems different from the macOS one).
Here's the web view color
