Coloring is based on a file supplied with the library. That file may or may not be complete. It is the compiler's ability to process the sketch that is important, not the color of the text on the screen.
If the compiler is able to compile, link, and upload a sketch, the IDE was able to find the library.
I ignored that difference and tried to run a sketch, but it wouldn't run.
Ignoring the lack of syntax coloring is fine. Failing to explain the "it wouldn't run" statement is not.
Was the compiler able to compile, link, and upload the sketch? What did you add to the sketch that involved the servo? What symptoms did the Arduino exhibit that caused you conclude that "it wouldn't run"?