What does "blue nose" and "red nose" even mean when referring to pit bulls?

I originally thought it just meant that they are blue in color or red in color... But now that I think about it... Are people seriously referring to the color of the nose? Like, black or pink nose??

So confused...
Update: I understand that they mean nothing, and all that. I agree. But I just never really understood what the people who acknowledge them are actually talking about...
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