The highlighting of words is not very important. They get highlighted because they are in some keyword file somewhere.
Anyway, that is the text editor program which recognises those words and colours them in for you, not the compiler.
As far as compilation is concerned, it matters what the compiler recognises, not the text editor.
If the compiler can find that avr header file, that's what it needs. It doesn't need to compile the code, the code is already compiled somewhere already. The necessary parts of the library ( which is already compiled ), is added to the compiled version of your program and any of your own libraries, to create the executable file ( or more specifically, the image of the executable file in the format for downloading to your actual arduino board ).