Chamois shed their coat from end of september till mid october - by rut (beginning of november) they are fully winter coated.

Basicaly coats differ in the length of the hair - summer short, winter long. Summer is normaly yelowish - red - brown, while winter is usually almost pure black on mid aged animals while young have more brownish and old more brownish-grey, very old almost silver-brown-grey. That is usually - not always. Some examples:

Summer coat

Winter coat

Old Chamois in winter coat: