Throughout the year
Throughout the world, depending on the participants.
Brad Davis played for United States in the 2014 FIFA World Cup.
Brad Davis had played 16 times for United States before the 2014 FIFA World Cup.
United State and Russia
Davis Cup was created in 1900.
According to the Davis Cup website (refer to the link, below), Tim Henman's very last opponent was Croatia* in the 2007 Davis Cup, in which he and the Great Britain Davis Cup team defeated Croatia, 4-1. * (technically speaking, Davis Cup tournaments are played by nations, not individuals)
The 2010 Davis cup final is not decided as yet.
Given that the Davis Cup recognizes only countries, not people,and since there are no countries named "black" (or, at least, none currently assigned to play the Davis Cup),the answer is: there have been no black winners of the Davis Cup.
Tennis is the sport associated with the Davis Cup.
Lithuania Davis Cup team was created in 1994.