Here in the UK, men traditionally wore dark suits, white shirts and black ties. But there is increasingly a growing trend towards dispensing with "mourning" attire - often at the request of the deceased's family in compliance with what their loved one would've wished. Moreover, a funeral service here, is now frequently described as being a 'Thanksgiving and Celebration' of the dead person's life. Which, all in all, would seem a less formal way of paying our final respects, yet is seen as an entirely fitting tribute.
Each nation has its own customs, of course. And it is usually the case that what is considered appropriate, will be determined by the environmental and climatic conditions of the country and/or region where the "rites of commemoration" are taking place.