Final answer:
The statement refers to the idea that a person's character and qualities are truly revealed when they are in a leadership position.
Step-by-step explanation:
The statement "You cannot know a man completely, his character, his principles, sense of judgment, not till he's shown his colors ruling the people" suggests that one's true nature and qualities are fully revealed only in positions of power or leadership. In this context, 'showing one's colors' means to display one's true traits or intentions, which might remain concealed during ordinary circumstances but become evident when a person is in a ruling or governing position.