How to change the font size, font in Visual studio Text editor. Also we can change background color

 Shortcut key to increase the size of Text

Ctrl+Alt+Mouse scroll OR Ctrl+Mouse scroll 

And

>Goto Tools>Option

>Under environment>Font and colors

>You can change font here

-----------------------------*************---------------------

we can also change background color :-

Goto Tools>Option

>Under environment>Font and colors

>Click on item background

reference:- https://docs.microsoft.com/en-us/visualstudio/ide/reference/how-to-change-fonts-and-colors-in-the-editor?view=vs-2019