I doubt Class::getDeclaredMethod() is able to find methods that a class inherited from any of its parents: 
Docs.Oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Class.html#getDeclaredMethod(java.lang.String,java.lang.Class...)
Instead, method colorCalc() is found declared inside class PGraphics: 
And not in any of its subclasses: 
Therefore, you’re gonna need to use PGraphics.class in place of g.getClass(). 