Clerical collars symbolise a life of challenge, service and deep fulfilment.
Clerical collars is know as a “dog collar”. It symbolises the fact that they are on a leash.
the “Dog Collar” as you put it, symbolizes in my mind, the purity of the vocation, where as the black symbolizes the vocation of priesthood. (by christyemily)
Black is cheap and can be made easily from any cloth. The Bishops traditional colour, green, was expensive and as for purple and scarlet these were always considered luxurious. In this day and age with cheep chemical dyes we tend to forget the practical origins of things. (by Penfold2)
Pastors wear their clergy collar and ministerial gown to symbolize the elevated status that God gives to the administering of the sacraments & preaching of the Word.
The clerical collar and gown is also a constant reminder to the pastor of his responsibility and accountability as a minister of the gospel and sacrament.