This will instantly change the Cortana search bar into the black. Scroll till the bottom till you find the option ‘ Choose your default app mode’.Open Personalization from the Settings Menu, and then select Colours from the left pane.This will launch the Windows 10 Settings. Click on Start Button and then click on the cog icon.You can switch to Dark mode, and your box will be black as well, but then the theme completely changes everything too dark mode. Windows 10 offers two modes – Dark and Light. Remember, these fixes will change all white search boxes to black, and one of the fixes need admin privileges. In this post, we will share a couple of tips which will allow you to set Cortana Search bar to black. Take a case of Taskbar which is usually dark, but when you look at Cortana search bar you will see that it has turned white. The Black Theme is one of the favorite themes of Windows 10 users, and if you see anything which is white it gets annoying.