Black chickens normally have a green gloss and matte black down. For breeds with yellow shanks, however, as is the case with the Leghorn, a lighter down colour is permitted.

Common faults are white in the plumage, red in the male plumage and a strong violet gloss.
Black birds with yellow shanks are possessed with a sex-linked gene which inhibits the black pigmentation in the legs. The male has this factor doubled-up and therefore has beautifully yellow shanks, while the female has a single factor and consequently her legs may have some dark stains.  Genetically, specimens with a lighter down colour will produce birds with cleaner shanks.
Black standard as well as bantam Leghorns are shown on a regular basis in the Netherlands.

Additional information