New
#21
*** see if your graphic card needs updating ***
I think your current issue either involves your monitors color correction settings or the same settings in your driver, or possibly something involving windows 10 themes. In windows XP there was a subset of options involving title bar fonts and colors/size for standard windows in the display properties near where you would change screen resolution and I'm pretty sure it also had something for selection color or opacity as well but I can't find the current windows 10 equivalent.. I'm sure it would bring about the solution to your problem if it isn't a color correction issue.
If such a setting can't be found then maybe your next best option is to try something that would modify a large quantity of the basic UI elements, I've seen others mention stardock elsewhere on the forums and while I haven't used any of their windows 10 offerings I would imagine there would be something that ends up tweaking the setting for selection opacity.