Blue is not really "blue". Blue is a dilution of black. And because this dilution is a recessive gene, it's also linked with health issues such as demodex mange. Furthermore, since it's only a dilution, "blue" noses can be seen in other breeds as well - and so can red noses - check out the Husky to the right! Nose colors aren't pit bull specific - and you wouldn't hear someone talking about their "Red-nose Husky"!
Color does not dictate temperament. We have heard some bizarre rumors about red, brindle, you-name-it-colored Pit Bulls being more aggressive - these are unfounded, untrue statements with no scientific evidence to support it.