There is no real significance to the color. What color to assign to certain words is defined in files delivered with libraries, called keywords.txt.
The problem is that every keywords.txt file on your system is read, whether you are using the library that the file comes with, or not.
The presence of a keywords.txt file with a library is not mandatory, so the usefullness of the color coding is just about zip, none, nada, zilch.