Over the centuries Church clerics were required to wear distinctive garb to identify them as ordained clergy. Particular dioceses or national bishops' conferences in various countries have established the norms for such clerical attire.
In the early Church, no distinctive garb seems to have been worn, except of course liturgical vestments, which in some cases were also worn outside the celebration of sacraments. For instance, sometimes bishops and priests wore the chasuble like regular clothing, as did the deacons with the dalmatic.
The color of the ordinary Roman cassock and clerical attire in general is black. For the regular parish priest, the cassock is totally black. For cardinals, the buttons, trim, and inside hem are scarlet silk; for patriarchs, archbishops, bishops, protonotaries apostolic and prelates of honor, the buttons, trim and inside hem are amaranth red; and for chaplains to the Holy Father, purple. (For liturgical and public ceremonies of the Church, cassocks are of one color; white for the Holy Father; scarlet for Cardinals; purple for patriarchs, archbishops, bishops, protonotaries apostolic, and prelates of honor: and black for priests. In some dioceses, especially in the tropics, permission is granted for cassocks to be white, and then trimmed in the color designating the status of the cleric.
The symbolism of the cassock is as follows; The Roman collar symbolizes obedience; the Sash or cincture around that waist, chastity; and the color black, poverty. Moreover, black is a color of mourning arid death for the priest, the symbolism is dying to oneself to rise and serve the Lord as well as giving witness of the Kingdom yet to come.
The Code of Canon Law still requires "clerics are to wear suitable ecclesiastical garb in accord with the norms issued by the conference of bishops and in accord with legitimate local custom" (No. 284). In our very secular world, the wearing of clerical garb continues to be a visible sign of belief and of the consecration of one's life to the service of the Lord and His Church.