In the Visual Effects list, select the “Custom” option, disable the “Shadow shadows under windows” option, and then click the “OK” button. On the Advanced tab of the System Properties window, click the “Settings” button in the Performance section. You can also head to Control Panel > System and Security > System > Advanced System Settings to launch it. To open it, hit Start, type “Advanced system settings” into the search box, and then press Enter. This setting is available in the old Advanced System Settings window.

Under the Choose Your Color section, disable the Automatically pick an accent color from my background option and choose your preferred color, instead. Windows 8 didn’t use shadows and had a clean, flat look with colored window borders, for example. To choose a custom window border color, head to Settings > Personalization > Colors.

However, you can turn these shadows off if you prefer. Windows 10 enables drop shadows for each window by default. You’ll see colored tabs in your title bars instead of fully colored title bars thanks to the Sets feature. To apply your accent color to your window borders, scroll down to the “Show accent color on the following surfaces” section, and then enable the “Title bars and window borders” option. Windows 10’s Redstone 5 update, which will be released to the stable Windows build sometime in Fall, 2018, uses a gray window border by default.

Windows 10 change border color