Passage: At the outer edge of the clock, golden Schwabacher numerals are set on a black background.  These numbers indicate Old Czech Time (or Italian hours), with 24 indicating the time of sunset, which varies during the year from as early as 16:00 in winter to 20:16 in summer.  This ring moves back and forth during the year to coincide with the time of sunset.

Question: What color background is the clock set on?
black