How do you turn off Razor highlighting in VS 2013?

Please see option that starts with HTML (i know its not obvious but does the trick).

Although the instructions on the accepted answer takes you to the correct settings that needs to be adjusted, it took a while for me to adjust the settings. So for those like me, the key is to change the Item Background property of the HTML Razor Code Background, but the background color you need to choose should be the same as that of Plain Text (the first item in Display Items list). Since I use dark theme, that default color of Plain Text wasn’t available for HTML Razor Code Background. So I had to go Custom… copy the color settings from Plain Text, and then got HTML Razor Code Background, Custom… and plugin those color setting number and now that highlight is gone!

You have to find Tools -> Options ->Environment -> Fonts and Colors -> HTML Razor Code Background to change it in VS 2013.