black coats, gartel)?

                                  Answer:
   
   The particular appearance is a matter of local custom for the group.
   
   Black Clothes:
          Black is the color of Gevurah (severity), and thus is a
          symbolically appropriate garb for serious and important events
          (praying, holidays, etc.) Those who wear such clothes all week
          are thus indicating that their daily life is also bound up in
          divrei yirah shamayim [fearing heaven].
          
          It is worth noting that black was the traditional colour of
          formal wear among many circles in the 18 Century CE. Hassidic
          garb is based on what the first Rebbes wore, and by and large
          represents the colours worn by Polish and other central
          Europeans.
          
   Gartel:
          It is required by the Shulchan Aruch (code of Jewish law) to
          have a separation between the top half of the body and the
          bottom while praying. Those who do not wear a gartel hold that
          other clothes satisfy the halacha; e.g., a regular belt or the
          waistband of his pants.
          
   Hat:
          A double head covering (and more complete head covering than a
          kippot) is used during davening. Some choose to wear it all the
          time, but it is not required. Some wear it while eating.
          
          The style of hat varies by groups, and the black hat is
          relatively modern. In the pre-war Lithuanian Yeshivot, grey
          suits and grey fedoras were the style and many in the Litvish
          tradition still wear grey and blue suits. In Jerusalem until
          the 1960s, Panama Hats were worn in the summer by some Haredim,
          and one very occasionally still sees Haredim wearing them.
          Right now in the yeshivah world, black suits and black
          [5]Borsalino hats seem to be de rigeur; yet it wasn't that long
          ago that many yeshivah bocherim wore black berets, and flat
          caps were not unknown.
          
   Some wear a (distinctive) gartel or hat (or simply a
   not-so-distinctive jacket) just for davening, to provide extra honor
   when talking to G-d. There is also a kabbalistic justification of the
   double head covering that refers to two distinct aspects of one's
   soul.