One of my favourite games on NG. There are different interpretation, imho:
1) People tend to have a black and white view of reality. That means they tend to differentiate between good/evil, right/wrong, etc., and do not consider that reality isn't black and white, but colored (or, to stay in the monochrome setting, there are different shades of gray). Keeping this into consideration allows you to have a better understanding of what's going on, but it's difficult: living with "absolutes" is far more simple. So, people who try to explain that reality is not that simple are often ignored. When the character is black or white people still listen to it; but when he goes gray (understanding the complexity of reality and refusing to simplify it as before), people start to ignore it.
2) The main character changes idea multiple times during the game, and convinces others though dialogue. However, people are more difficult to convince after every "idea-change": it's like they remember the protagonist, and don't understand why it changed its mind. At the end, they stop listening the main character: it has changed idea too many times, and people consider it unreliable. They don't trust it anymore, for it has changed its mind too many times. How will they know that it won't change its mind again, continuing to send them back and forth? In this interpretation, the gray color doesn't represent a "gray area" of thinking, but the character losing its ability to communuicate with others.
These two interpretations are alternatives.
Anyway, great game!!