I am currently using the genieArduino library for a project.
I have #include <genieArduino.h> in my code.
Shouldn't the genie.Begin(Serial1) automatically "highlight" the word "Begin" and genie.AttachEventHandler(myGenieEventHandler) automatically "highlight" the word "AttachEventHandler" as shown in the image?
I thought that when you #include a library, the IDE automatically "highlights" functions, methods, key words, etc.
No, it's not automatic. The library must define the keywords of the library in a specially formatted file named keywords.txt. Some library authors don't bother to do that (as is the case with the genieArduino library. Some library authors define keywords, but then don't bother to update the file as the library API evolves, so the keywords are incompletely defined. Some library authors attempt to define keywords, but don't correctly format the file, so the keywords aren't recognized by the Arduino IDE.
Keyword highlighting is merely cosmetic. The Arduino IDE's keyword highlighting system is very crude. You shouldn't put much importance on the colors of words in the Arduino IDE.