I don't see any error on your code, everything is well written and simple. Except trying putting PUBLIC on your Class displayer. If you encounter the same problem again try to rebuild your whole code and try to recompile the whole code. Even try restarting your personal computer.
Answer:
theme colors
Explanation:
As said, a group of colors that are used to format text and objects in a document. When you open the Color menu, these colors determine what you see.