US Standard:
Nose - black, except in blue merles where black noses are preferred but butterfly noses
are tolerated. A nose other than solid black in any other color is a disqualification.
Butterfly
Nose:
Same dog, same nose, pictures left taken 6 months apart, picture right taken at 3 years.
Notice the change in the black pigmentation. Most time the colour of a
butterfly nose in blue merles darkens with aging.
The American standard allows a
butterfly nose in blue merles, the British does not.
Liver nose:
Two examples of liver coloured noses. This is not according to the standard.