That got me thinking it must have to do with St Nicholas being a bishop. Then I found this:
Liturgical gloves (chirothecœ, called also at an earlier date manicœ, wanti,) are a liturgical adornment reserved for bishops and cardinals. Other ecclesiastics, including abbots, cannot use them without a special papal privilege. They are worn only at a pontifical Mass, never at any other function, and then only to the washing of the hands before the Sacrifice.
The colour of the gloves must correspond with the liturgical colour of the feast or day in the services of which they are worn; episcopal gloves, however, are never black, as they are not used on Good Friday nor at the celebration of Masses for the dead.Awesome! And now you know how to answer that question if your kid asks. :)