Where did the white and liver come from

From "THE NEW MINIATURE SCHNAUZER, THE BREED SINCE CH. DOREM DISPLAY" by Dan Kiedrowski:

The oldest Miniature Schnauzer registered was a black bitch, Findel, whelped in October 1888. Of the first eight bitches registered in the first volume, three were black, three were yellow, one black and tan and only one was described as pepper and salt. The six males included no blacks. Four were yellow of various shades, one was black and tan and again only one was pepper and salt.

Also quoted:

Leda Martin recalled Flieger (an imported dog she speaks of below) as follows:

In 1930, I imported Flieger Heinzelmannchen. He died before he gained his title, but fortunately sired a few puppies. He was a lovely gray salt and pepper, and threw his color in a day when the majority of our dogs were cinnamon, black and tan or black and silver, or a rather unpleasant combination of the three...